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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
                                  SCHEDULE TO
                                 (RULE 14d-100)
                 TENDER OFFER STATEMENT UNDER SECTION 14(d)(1)
           OR SECTION 13(e)(1) OF THE SECURITIES EXCHANGE ACT OF 1934
                            ------------------------

                         BARRETT RESOURCES CORPORATION
                       (NAME OF SUBJECT COMPANY (ISSUER))

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.
                      (NAMES OF FILING PERSONS (OFFERORS))
                            ------------------------
                     COMMON STOCK, PAR VALUE $.01 PER SHARE
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                         (TITLE OF CLASS OF SECURITIES)
                            ------------------------
                                   068480201

                     (CUSIP NUMBER OF CLASS OF SECURITIES)

                           WILLIAM G. VON GLAHN, ESQ.
                   SENIOR VICE PRESIDENT AND GENERAL COUNSEL
                          THE WILLIAMS COMPANIES, INC.
                              ONE WILLIAMS CENTER
                             TULSA, OKLAHOMA 74172
                           TELEPHONE: (918) 573-2000
  (NAME, ADDRESS AND TELEPHONE NUMBER OF PERSON AUTHORIZED TO RECEIVE NOTICES
                AND COMMUNICATIONS ON BEHALF OF FILING PERSONS)

                                WITH A COPY TO:

                             MORRIS J. KRAMER, ESQ.
                           RICHARD J. GROSSMAN, ESQ.
                    SKADDEN, ARPS, SLATE, MEAGHER & FLOM LLP
                               FOUR TIMES SQUARE
                               NEW YORK, NY 10036
                            TELEPHONE: 212-735-3000

                           CALCULATION OF FILING FEE

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                TRANSACTION VALUATION*                                  AMOUNT OF FILING FEE
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                    $1,221,326,646                                            $244,265
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*   Estimated for purposes of calculating the amount of the filing fee only. The
    amount assumes the purchase of a total of 16,730,502 shares of the
    outstanding common stock, par value $0.01 per share, at a price per share of
    $73.00 in cash. The amount of the filing fee calculated in accordance with
    Rule 0-11 of the Securities Exchange Act of 1934, as amended, equals 1/50 of
    1% of the transaction value.

[ ]  Check the box if any part of the fee is offset as provided by Rule
     0-11(a)(2) and identify the filing with which the offsetting fee was
     previously paid. Identify the previous filing by registration statement
     number or the Form or Schedule and the date of its filing.

                                               
Amount Previously Paid: None                      Filing party: N/A
Form or Registration No.: N/A                     Date Filed: N/A

[ ]  Check the box if the filing relates solely to preliminary communications
made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the
statement relates:

     [X]  third-party tender offer subject to Rule 14d-1.
     [ ]  issuer tender offer subject to Rule 13e-4.
     [ ]  going-private transaction subject to Rule 13e-3.
     [ ]  amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results
of the tender offer:  [ ]
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ITEM 1.  SUMMARY TERM SHEET

      The information set forth in the section of the Offer to Purchase entitled
"Summary Term Sheet" is incorporated herein by reference.

ITEM 2.  SUBJECT COMPANY INFORMATION.

      (a) The name of the subject company is Barrett Resources Corporation, a
Delaware corporation ("Barrett Resources"), and the principal executive offices
are located at 1515 Arapahoe Street, Tower 3, Suite 1000, Denver, CO 80202. Its
telephone number at such offices is (303) 572-3900.

      (b) This Statement relates to the offer by Resources Acquisition Corp.
("Purchaser"), a Delaware corporation and a wholly-owned subsidiary of The
Williams Companies, Inc., a Delaware corporation ("Williams"), to purchase
16,730,502 shares of common stock of Barrett Resources, par value $.01 per share
(including the associated preferred stock purchase rights, the "Shares"), at
$73.00 per Share, net to the seller in cash, upon the terms and subject to the
conditions set forth in the Offer to Purchase and in the related Letter of
Transmittal, copies of which are attached hereto as Exhibits (a)(l) and (a)(2)
(which are herein collectively referred to as the "Offer"). The information set
forth in the introduction to the Offer to Purchase (the "Introduction") and on
the cover page is incorporated herein by reference.

      (c) The information concerning the principal market in which the Shares
are traded and certain high and low sales prices for the Shares in such
principal market is set forth in Section 6, "Price Range of the Shares;
Dividends" of the Offer to Purchase and is incorporated herein by reference.

ITEM 3.  IDENTITY AND BACKGROUND OF THE FILING PERSON.

      (a), (b), (c) The information set forth in Section 9, "Certain Information
Concerning Williams and Purchaser", and Schedule I of the Offer to Purchase is
incorporated herein by reference.

ITEM 4.  TERMS OF THE TRANSACTION.

      (a)(1)(i)-(viii), (xii) The information set forth under (a)
"Introduction", (b) Section 1, "Terms of the Offer", (c) Section 5, "Material
United States Federal Income Tax Consequences", (d) Section 7, "Possible Effects
of the Offer on the Market for the Shares; NYSE Listing; Exchange Act
Registration; Margin Regulations", (e) Section 8, "Certain Information
Concerning Barrett Resources", (f) Section 10, "Background of the Offer", (g)
Section 11, "Purpose of the Offer and the Merger; the Merger Agreement; Effects
of Inability to Consummate the Merger; Statutory Requirements; Appraisal Rights;
Plans for Barrett Resources; Confidentiality Agreements; "Going Private"
Transactions", (h) Section 12, "Source and Amount of Funds" and (i) Section 14,
"Conditions of the Offer" of the Offer to Purchase is incorporated herein by
reference. No subsequent offering period will be offered.

      (a)(1) (x) and (xi) Not applicable.

      (a)(2)(i)-(iv), (vii) The information set forth under (a) "Introduction",
(b) Section 1, "Terms of the Offer", (c) Section 5, "Material United States
Federal Income Tax Consequences", (d) Section 7, "Possible Effects of the Offer
on the Market for the Shares; NYSE Listing; Exchange Act Registration; Margin
Regulations", (e) Section 8, "Certain Information Concerning Barrett Resources",
(f) Section 10, "Background of the Offer", (g) Section 11, "Purpose of the Offer
and the Merger; the Merger Agreement; Effects of Inability to Consummate the
Merger; Statutory Requirements; Appraisal Rights; Plans for Barrett Resources;
Confidentiality Agreements; "Going Private" Transactions", (h) Section 12,
"Source and Amount of Funds" and (i) Section 14, "Conditions of the Offer" of
the Offer to Purchase is incorporated herein by reference.

      (a)(2) (v) and (vi) Not applicable.

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ITEM 5.  PAST CONTACTS, TRANSACTIONS, NEGOTIATIONS AND AGREEMENTS.

      The information set forth in (a) Section 9, "Certain Information
Concerning Williams and Purchaser", (b) Section 10, "Background of the Offer"
and (c) Section 11, "Purpose of the Offer and the Merger; the Merger Agreement;
Effects of Inability to Consummate the Merger; Statutory Requirements; Appraisal
Rights; Plans for Barrett Resources" of the Offer to Purchase is incorporated
herein by reference.

ITEM 6.  PURPOSE OF THE TENDER OFFER AND PLANS OR PROPOSALS.

      (a), (c)(1), (c)(3)-(7) The information set forth in (a) "Introduction",
(b) Section 6, "Price Range of the Shares; Dividends", (c) Section 7, "Possible
Effects of the Offer on the Market for the Shares; NYSE Listing; Exchange Act
Registration; Margin Regulations" and (d) Section 11, "Purpose of the Offer and
the Merger; the Merger Agreement; Effects of Inability to Consummate the Merger;
Statutory Requirements; Appraisal Rights; Plans for Barrett Resources;
Confidentiality Agreements; " 'Going Private' Transactions" of the Offer to
Purchase is incorporated herein by reference.

      (c)(2) None.

ITEM 7.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

      (a), (d) The information set forth in Section 12, "Source and Amount of
Funds" of the Offer to Purchase is incorporated herein by reference.

      (b) Not applicable.

ITEM 8.  INTEREST IN SECURITIES OF THE SUBJECT COMPANY.

      The information set forth in "Introduction", Section 8, "Certain
Information Concerning Barrett Resources", and Schedule I of the Offer to
Purchase is incorporated herein by reference.

ITEM 9.  PERSONS/ASSETS, RETAINED, EMPLOYED, COMPENSATED OR USED.

      The information set forth in "Introduction" and Section 16, "Fees and
Expenses" of the Offer to Purchase is incorporated herein by reference.

ITEM 10.  FINANCIAL STATEMENTS.

      Not applicable.

ITEM 11.  ADDITIONAL INFORMATION.

      The information set forth in (a) Section 7, "Possible Effects of the Offer
on the Market for the Shares; NYSE Listing; Exchange Act Registration; Margin
Regulations", (b) Section 11, "Purpose of the Offer and the Merger; the Merger
Agreement; Effects of Inability to Consummate the Merger; Statutory
Requirements; Appraisal Rights; Plans for Barrett Resources; Confidentiality
Agreements; " 'Going Private' Transactions", (c) Section 15, "Legal Matters;
Required Regulatory Approvals" and (d) Section 17, "Miscellaneous" of the Offer
to Purchase is incorporated herein by reference.

ITEM 12.  EXHIBITS.

     
(a)(1)  Offer to Purchase dated May 14, 2001.
(a)(2)  Letter of Transmittal.
(a)(3)  Notice of Guaranteed Delivery.
(a)(4)  Letter to Brokers, Dealers, Commercial Banks, Trust
        Companies and Other Nominees.
(a)(5)  Letter to Clients for use by Brokers, Dealers, Commercial
        Banks, Trust Companies and Other Nominees.

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(a)(6)  Guidelines for Certification of Taxpayer Identification
        Number on Substitute Form W-9.
(a)(7)  Press Release issued by Williams on May 7, 2001,
        incorporated herein by reference to the Pre-commencement
        Schedule TO filed by Williams on May 7, 2001.
(a)(8)  Summary Advertisement as published in The Wall Street
        Journal on May 14, 2001.
(a)(9)  Press Release issued by Williams on May 14, 2001.
(d)(1)  Agreement and Plan of Merger, dated as of May 7, 2001, by
        and among Williams, Purchaser and Barrett Resources.
(d)(2)  Confidentiality Agreement, dated as of March 9, 2001, by and
        between Williams and Barrett Resources.
(d)(3)  Nondisclosure Agreement, dated as of May 6, 2001, by and
        between Barrett Resources and Williams.
(g)     Not applicable.
(h)     Not applicable.

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                                   SIGNATURE

      After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

                                          RESOURCES ACQUISITION CORP.

                                          By: /s/ RALPH A. HILL
                                          --------------------------------------
                                          Name: Ralph A. Hill
                                          Title: Senior Vice President

                                          THE WILLIAMS COMPANIES, INC.

                                          By: /s/ KEITH E. BAILEY
                                          --------------------------------------
                                          Name: Keith E. Bailey
                                          Title: Chairman, President and Chief
                                                 Executive Officer

Dated: May 14, 2001

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                                 EXHIBIT INDEX

EXHIBIT
  NO.                             EXHIBIT NAME
- -------                           ------------
                                                                    
(a)(1)    Offer to Purchase dated May 14, 2001........................
(a)(2)    Letter of Transmittal.......................................
(a)(3)    Notice of Guaranteed Delivery...............................
(a)(4)    Letter to Brokers, Dealers, Commercial Banks, Trust
          Companies and Other Nominees................................
(a)(5)    Letter to Clients for use by Brokers, Dealers, Commercial
          Banks, Trust Companies and Other Nominees...................
(a)(6)    Guidelines for Certification of Taxpayer Identification
          Number on Substitute Form W-9...............................
(a)(7)    Press Release issued by Williams on May 7, 2001,
          incorporated herein by reference to the Pre-Commencement
          Schedule TO filed by Williams on May 7, 2001................
(a)(8)    Summary Advertisement as published in The Wall Street
          Journal on May 14, 2001.....................................
(a)(9)    Press Release issued by Williams on May 14, 2001............
(d)(1)    Agreement and Plan of Merger, dated as of May 7, 2001, by
          and among Williams, Purchaser and Barrett Resources.........
(d)(2)    Confidentiality Agreement, dated as of March 9, 2001, by and
          between Williams and Barrett Resources......................
(d)(3)    Nondisclosure Agreement, dated as of May 6, 2001, by and
          between Barrett Resources and Williams.
(g)       Not applicable..............................................
(h)       Not applicable..............................................

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                                                               Exhibit (a)(1)

                           OFFER TO PURCHASE FOR CASH

                       16,730,502 SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       AT

                              $73.00 NET PER SHARE

                                       BY

                          RESOURCES ACQUISITION CORP.
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.

        THE OFFER, PRORATION PERIOD AND WITHDRAWAL RIGHTS WILL EXPIRE AT
            12:00 MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11, 2001,
                         UNLESS THE OFFER IS EXTENDED.

      The Offer (as defined herein) is being made pursuant to an Agreement and
Plan of Merger, dated as of May 7, 2001, by and among The Williams Companies,
Inc. ("Williams"), Resources Acquisition Corp. ("Purchaser") and Barrett
Resources Corporation ("Barrett Resources"). The Board of Directors of Barrett
Resources has unanimously approved the Merger Agreement and the transactions
contemplated thereby, including the Offer and the Merger (as defined herein),
and has unanimously determined that the Offer and the Merger are advisable and
fair to, and in the best interests of, Barrett Resources' stockholders and
unanimously recommends that stockholders accept the Offer and tender their
Shares (as defined herein) pursuant to the Offer and approve the Merger at the
time of the Barrett Resources Special Meeting (as defined herein). If the Offer
and the Merger are completed, Purchaser will purchase 16,730,502 Shares in the
Offer at a price of $73.00 per Share and holders of the remaining Shares
(including any Shares returned to tendering stockholders as a result of
proration) will receive 1.767 shares of Williams Common Stock (as defined
herein) for each Share in the Merger.

      THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, (1) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION DATE (AS DEFINED HEREIN) AT
LEAST 16,730,502 SHARES, AND (2) THE EXPIRATION OR TERMINATION OF THE WAITING
PERIOD UNDER THE HART-SCOTT-RODINO ANTITRUST IMPROVEMENTS ACT OF 1976, AS
AMENDED, AND THE RULES AND REGULATIONS PROMULGATED THEREUNDER. THE OFFER IS ALSO
SUBJECT TO THE OTHER CONDITIONS SET FORTH IN THIS OFFER TO PURCHASE. THE OFFER
IS NOT SUBJECT TO A FINANCING CONDITION. SEE SECTION 14.

      A summary of the principal terms of the Offer appears on pages (iii)
through (viii). You should read this entire document carefully before deciding
whether to tender your Shares.

                      The Dealer Manager for the Offer is:

                              MERRILL LYNCH & CO.

May 14, 2001
   2

                                   IMPORTANT

      If you want to tender all or some of your Shares, you should either (i)
complete and sign the enclosed Letter of Transmittal (or facsimile thereof) by
following the Instructions in the Letter of Transmittal, have your signature on
the Letter of Transmittal guaranteed (if required by Instruction 1 to the Letter
of Transmittal), mail or deliver the Letter of Transmittal (or a facsimile
thereof) and any other required documents to the Depositary (as defined herein)
and either deliver the certificates for the Shares you are tendering to the
Depositary or tender the Shares by book-entry transfer as described in Section 3
of this Offer to Purchase or (ii) request that your broker, dealer, commercial
bank, trust company or other nominee tender your Shares for you. If your Shares
are registered in the name of a broker, dealer, commercial bank, trust company
or other nominee, you must contact that broker, dealer, commercial bank, trust
company or other nominee in order for them to tender your Shares.

      If you want to tender Shares but the certificates for your Shares are not
immediately available, or if you cannot tender by book-entry transfer or cannot
deliver all required documents to the Depositary before the Offer expires, you
can tender your Shares by following the procedures for guaranteed delivery that
are described in Section 3 of this Offer to Purchase.

      Questions and requests for assistance can be made to the Dealer Manager or
the Information Agent at their respective address and telephone numbers on the
back cover of this Offer to Purchase. Requests for additional copies of this
Offer to Purchase, the Letter of Transmittal, the Notice of Guaranteed Delivery
and other tender offer materials can be made to the Dealer Manager or the
Information Agent or brokers, dealers, commercial banks or trust companies.

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                               TABLE OF CONTENTS

                                                              PAGE
                                                              ----
                                                           
SUMMARY TERM SHEET..........................................  -iii-
INTRODUCTION................................................   -1-
   1.  TERMS OF THE OFFER...................................   -4-
   2.  ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES;
       PRORATION............................................   -6-
   3.  PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING
       SHARES...............................................   -7-
   4.  WITHDRAWAL RIGHTS....................................  -10-
   5.  MATERIAL UNITED STATES FEDERAL INCOME TAX
       CONSEQUENCES.........................................  -11-
   6.  PRICE RANGE OF THE SHARES; DIVIDENDS.................  -14-
   7.  POSSIBLE EFFECTS OF THE OFFER ON THE MARKET FOR THE
       SHARES; NYSE LISTING; EXCHANGE ACT REGISTRATION;
       MARGIN REGULATIONS...................................  -14-
   8.  CERTAIN INFORMATION CONCERNING BARRETT RESOURCES.....  -16-
   9.  CERTAIN INFORMATION CONCERNING WILLIAMS AND
       PURCHASER............................................  -22-
  10.  BACKGROUND OF THE OFFER..............................  -23-
  11.  PURPOSE OF THE OFFER AND THE MERGER; THE MERGER
       AGREEMENT; EFFECTS OF INABILITY TO CONSUMMATE THE
       MERGER; STATUTORY REQUIREMENTS; APPRAISAL RIGHTS;
       PLANS FOR BARRETT RESOURCES; CONFIDENTIALITY
       AGREEMENTS; "GOING PRIVATE" TRANSACTIONS.............  -28-
  12.  SOURCE AND AMOUNT OF FUNDS...........................  -42-
  13.  DIVIDENDS AND DISTRIBUTIONS..........................  -43-
  14.  CONDITIONS OF THE OFFER..............................  -43-
  15.  LEGAL MATTERS; REQUIRED REGULATORY APPROVALS.........  -45-
  16.  FEES AND EXPENSES....................................  -47-
  17.  MISCELLANEOUS........................................  -48-

SCHEDULE I
  DIRECTORS AND EXECUTIVE OFFICERS OF
  WILLIAMS AND PURCHASER....................................  -49-

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                               SUMMARY TERM SHEET

      The Williams Companies, Inc. ("Williams"), through its wholly-owned
subsidiary, Resources Acquisition Corp. ("Purchaser", "we" or "us"), is offering
to purchase (the "Offer") 16,730,502 shares of the common stock, par value $0.01
per share (including the associated preferred stock purchase rights, the
"Shares") of Barrett Resources Corporation ("Barrett Resources") for $73.00 per
Share, net to you in cash, pursuant to an Agreement and Plan of Merger, dated as
of May 7, 2001, by and among Williams, Purchaser and Barrett Resources (the
"Merger Agreement"). The following are some of the questions you, as a
stockholder of Barrett Resources, may have and answers to those questions. You
should carefully read this Offer to Purchase and the accompanying Letter of
Transmittal in their entirety because the information in this summary term sheet
is not complete and additional important information is contained in the
remainder of this Offer to Purchase and the Letter of Transmittal.

WHO IS OFFERING TO BUY MY SECURITIES? WHY?

      Our name is Resources Acquisition Corp. We are a Delaware corporation
formed for the purpose of making a tender offer for the Shares and consummating
the acquisition of Barrett Resources. We are a wholly-owned subsidiary of The
Williams Companies, Inc., a Delaware corporation whose shares of common stock
are listed on the New York Stock Exchange ("NYSE"). This tender offer is the
first step in Williams' plan to acquire all of the outstanding Shares of Barrett
Resources on the terms provided for in the Merger Agreement. See "Introduction".

WHAT ARE THE CLASSES AND AMOUNTS OF SECURITIES SOUGHT IN THE OFFER?

      We are seeking to purchase 16,730,502 of the outstanding Shares of Barrett
Resources for $73.00 per Share, net to you in cash. See "Introduction".

WHAT IS THE PURPOSE OF THE OFFER?

      The purpose of the Offer is to enable Williams to acquire approximately
50% of the outstanding Shares. Following the Offer, Purchaser and Williams
intend to acquire the remaining capital stock of Barrett Resources that was not
acquired in the Offer in a merger transaction. See "Introduction" and Section
11, "Purpose of the Offer and the Merger" and "-- Plans for Barrett Resources".

IF PURCHASER SUCCEEDS IN PURCHASING THE SHARES OF BARRETT RESOURCES IT IS
SEEKING TO BUY IN THE OFFER, WHAT WILL HAPPEN TO MY REMAINING SHARES AFTER THE
OFFER?

      If we accept for payment and pay for 16,730,502 Shares, Barrett Resources
is expected to be merged with and into us. Additionally, if we accept for
payment and pay for 16,730,502 Shares, we would effectively have sufficient
voting power to approve the merger without the affirmative vote of other
stockholders of Barrett Resources. Barrett Resources, as a result, would become
a wholly-owned subsidiary of Williams. If the merger takes place, Williams will
own all of the capital stock of Barrett Resources and all remaining stockholders
(other than Barrett Resources, Williams, Purchaser, or other subsidiaries of
Williams) will receive shares of Williams common stock in exchange for each of
their Shares.

WHAT WILL BE PAID TO STOCKHOLDERS OF BARRETT RESOURCES IN THE MERGER AND WHAT IS
THE FORM OF PAYMENT?

      Williams will issue 1.767 shares of its common stock in the merger in
exchange for each Share. Based on the closing sale price of the Williams common
stock on the NYSE on Friday, May 4, 2001, the last full trading day before the
date of announcement of the execution of the Merger Agreement, the 1.767 shares
of Williams common stock that would be issued for each Share in the merger had a
value of $73.63. Based on the closing sale price of Williams common stock on the
NYSE on Friday, May 11, 2001, the last full NYSE trading day before the date of
this Offer to Purchase, the 1.767 shares of Williams common stock that would be
issued for each Share in the merger had a value of $71.09.

                                       iii
   5

THE MARKET VALUE OF THE SHARES OF WILLIAMS COMMON STOCK THAT YOU AS A BARRETT
RESOURCES STOCKHOLDER WOULD RECEIVE IN THE MERGER WILL VARY AS A RESULT OF THE
FIXED EXCHANGE RATIO AS THE WILLIAMS COMMON STOCK PRICE FLUCTUATES.

      The exchange ratio of 1.767 shares of Williams common stock per Barrett
Resources Share is a fixed ratio that will not be adjusted as a result of any
increase or decrease in the market price of either shares of Williams common
stock or Barrett Resources Shares. The market price of shares of Williams common
stock at the time the merger is completed may be higher or lower than the price
on the date of this document, on the date of completion of the Offer and on the
date of the special meeting of stockholders of Barrett Resources to be held to
vote on the merger. Various factors may affect the price of shares of Williams
common stock, including:

      - changes in the business, operations, or prospects of Barrett Resources
        or Williams;

      - market assessments of the benefits of the merger and of the likelihood
        that the merger will be completed; and

      - general market, industry and economic conditions.

To a large extent, these factors are beyond our control, Williams' control or
the control of Barrett Resources.

      Because the merger will be completed only after the special meeting of
Barrett Resources stockholders, there is no way to be sure that the price of the
shares of Williams common stock now, at the time of the completion of the Offer
or on the date of the special meeting, will be indicative of its price when the
merger is completed. The market price of Williams common stock may increase and
decrease significantly before and after completion of the merger. As a result,
the Williams common stock you as a Barrett Resources stockholder receive in the
merger may be worth more or less than the price being offered for the Shares in
the Offer. WE URGE YOU TO OBTAIN CURRENT MARKET QUOTATIONS FOR BOTH BARRETT
RESOURCES SHARES AND SHARES OF WILLIAMS COMMON STOCK BEFORE DECIDING WHETHER TO
TENDER YOUR SHARES.

WHAT WILL HAPPEN IF MORE THAN 16,730,502 SHARES ARE VALIDLY TENDERED AND NOT
WITHDRAWN PRIOR TO THE EXPIRATION DATE OF THE OFFER?

      If more than 16,730,502 Shares are validly tendered and not withdrawn
prior to the expiration date of the Offer (the "Expiration Date"), we will
accept for payment and pay for only 16,730,502 Shares on a pro rata basis (with
appropriate adjustments to avoid purchase of fractional Shares) based on the
number of Shares properly tendered by each stockholder prior to or on the
Expiration Date.

HOW MUCH ARE YOU OFFERING TO PAY FOR MY SHARES IN THE OFFER AND WHAT IS THE FORM
OF PAYMENT? WILL I HAVE TO PAY ANY FEES OR COMMISSIONS?

      We are offering to pay $73.00 per Share in the Offer, net to you in cash.
If you tender your Shares to us in the Offer, you will not have to pay brokerage
fees, commissions or similar expenses. However, if you own your Shares through a
broker or other nominee, and your broker tenders your Shares on your behalf,
your broker or nominee may charge you a fee for doing so. You should consult
your broker or nominee to determine whether any charges will apply.

WHAT ARE THE TAX CONSEQUENCES OF THE SALE OF SHARES TO PURCHASER THROUGH THE
OFFER?

      The sale of Shares to Purchaser through the Offer is a taxable transaction
for United States federal income tax purposes, and may also be taxable under
applicable state, local and other tax laws. If you sell all of your Shares to
Purchaser through the Offer, you will recognize a gain or loss equal to the
difference between the amount of cash that you receive from Purchaser for the
Shares and your tax basis in such Shares.

                                        iv
   6

      Even if you tender all of your Shares in the Offer, you may have some but
not all of your tendered Shares accepted for purchase by us pursuant to the
terms of the Offer, as a result of proration. Where you sell some of your Shares
to us through the Offer and exchange the rest of your Shares for Williams common
stock pursuant to the merger of Barrett Resources with and into us, you will
recognize gain (but not loss) equal to the lesser of (i) the amount of cash you
receive pursuant to the Offer and (ii) an amount equal to the excess, if any, of
(a) the sum of the amount of cash you receive pursuant to the Offer and the fair
market value of the Williams common stock you receive pursuant to the merger
over (b) the tax basis of your Shares.

      If certain conditions relating to the United States federal income tax
treatment of the Offer and the merger of Barrett Resources with and into us are
not met, then we may, at Williams' reasonable discretion, be merged with and
into Barrett Resources. In this case, instead of the tax consequences described
in the immediately preceding paragraph, you will recognize all of your gain or
loss on the disposition of your Shares in the Offer and/or such a reverse
merger.

      We encourage you to consult your own tax advisor about the effect the
Offer will have on you. See Section 5, "Material United States Federal Income
Tax Consequences".

WHAT ARE THE TAX CONSEQUENCES OF THE MERGER?

      In general, if you do not sell any of your Shares to us through the Offer
and exchange all of your Shares for Williams common stock pursuant to the merger
of Barrett Resources with and into us, you will not recognize any gain or loss
on the exchange except with respect to any cash you receive in lieu of a
fractional share of Williams common stock. If you sell some of your Shares to us
through the Offer and exchange the rest of your Shares for Williams common stock
pursuant to the merger of Barrett Resources with and into us, you will recognize
gain (but not loss) equal to the lesser of (i) the amount of cash you receive
pursuant to the Offer and (ii) an amount equal to the excess, if any, of (a) the
sum of the amount of cash you receive pursuant to the Offer and the fair market
value of the Williams common stock you receive pursuant to the merger over (b)
the tax basis of your Shares.

      If certain conditions relating to the United States federal income tax
treatment of the Offer and the merger of Barrett Resources with and into us are
not met, then Purchaser may, at Williams' reasonable discretion, be merged with
and into Barrett Resources. In this case, instead of the tax consequences
described in the immediately preceding paragraph, you will recognize all of your
gain or loss on the disposition of your Shares in the Offer and/or such a
reverse merger.

      We encourage you to consult your own tax advisor about the effect the
merger will have on you. See Section 5, "Material United States Federal Income
Tax Consequences".

DOES PURCHASER HAVE THE FINANCIAL RESOURCES TO MAKE PAYMENT?

      Yes. We will need approximately $1.23 billion to purchase the 16,730,502
Shares we are seeking to buy in the Offer and to pay related fees and expenses.
In addition, Barrett Resources has agreed in the Merger Agreement to seek the
consent of the bank lenders under its credit agreement to permit it to
consummate the transactions contemplated by the Merger Agreement without
repaying the indebtedness under its credit agreement. If such bank consents are
not obtained, Williams would need approximately $145 million of additional funds
to repay the indebtedness under the credit agreement. It is anticipated that
such funds will be obtained by Williams under its existing commercial paper
program and revolving credit agreements. If we are unable to utilize the
foregoing financing arrangements, Williams will seek alternative financing. See
Section 12, "Source and Amount of Funds".

IS WILLIAMS' FINANCIAL CONDITION RELEVANT TO MY DECISION TO TENDER IN THE OFFER?

      Because the form of payment in the Offer consists solely of cash and the
Offer is not subject to a financing condition, we do not think Williams'
financial condition is material to your decision as to whether to tender in the
Offer. However, as noted above, if the Offer is completed you would receive, for

                                        v
   7

each Share you continue to hold after the Offer, 1.767 shares of Williams common
stock in the subsequent merger, which may have a market value higher or lower
than $73.00 at the time of the merger. If you would like additional information
about Williams' financial condition, please see Section 9, "Certain Information
Concerning Williams and Purchaser".

HAS THE BOARD OF DIRECTORS OF BARRETT RESOURCES APPROVED THE MERGER?

      Yes. The Board of Directors of Barrett Resources convened a meeting on May
7, 2001 and unanimously approved the Offer and merger on the terms set forth in
the Merger Agreement. Barrett Resources' financial advisors, Goldman, Sachs &
Co. and Petrie Parkman & Co., Inc., each delivered a written opinion dated May
7, 2001 to the Board of Directors that, as of that date and on the basis of and
subject to the matters described in such opinion, the consideration to be
received by Barrett Resources' stockholders in the Offer and merger, taken
together, was fair from a financial point of view to those stockholders.

HOW LONG DO I HAVE TO DECIDE WHETHER TO TENDER IN THE OFFER?

      You have until at least 12:00 midnight, eastern time, on Monday, June 11,
2001, to tender your Shares in the Offer. If you cannot deliver everything
required to make a valid tender to EquiServe Trust Company, N.A. ("EquiServe"),
the depositary for the Offer, prior to such time, you may be able to use a
guaranteed delivery procedure, which is described in Section 3, "Procedures for
Accepting this Offer and Tendering Shares".

CAN THE OFFER BE EXTENDED AND, IF SO, UNDER WHAT CIRCUMSTANCES?

      Unless the Merger Agreement is previously terminated in accordance with
its terms, if the conditions to the Offer are not satisfied on the scheduled
Expiration Date of the Offer, the Expiration Date would be extended to a later
date, but in no event later than August 31, 2001. See Section 14, "Conditions of
the Offer". Such conditions include that (i) there be validly tendered and not
withdrawn at least 16,730,502 Shares (we call this condition the "Minimum
Condition") and (ii) the waiting period under applicable antitrust laws shall
have expired or been terminated.

HOW WILL I BE NOTIFIED IF THE OFFER IS EXTENDED?

      If we decide to extend the Offer, at the time the Offer is currently
scheduled to expire we will inform EquiServe, the depositary for the Offer, of
that fact and will make a public announcement of the extension not later than
9:00 a.m., eastern time, on the next business day after the day on which the
Offer was previously scheduled to expire.

WHAT ARE THE MOST SIGNIFICANT CONDITIONS TO THE OFFER?

      We are not obligated to purchase any Shares which are validly tendered
unless at least 16,730,502 Shares are validly tendered and not withdrawn. In
addition, our obligation to purchase Shares in the Offer is conditioned upon,
among other things, the expiration or termination of the applicable waiting
period under applicable antitrust laws. See Section 14, "Conditions of the
Offer".

HOW DO I TENDER MY SHARES?

      To tender Shares, you must deliver the certificates representing your
Shares, together with a completed Letter of Transmittal, to EquiServe, the
depositary for the Offer, not later than the Expiration Date. If your Shares are
held in street name by your broker, dealer, bank, commercial bank, trust company
or other nominee, such nominee can tender your Shares for you. If you cannot
deliver everything required to make a valid tender to the depositary prior to
the Expiration Date, you may have a limited amount of additional time to tender
by having a broker, a bank or other fiduciary which is a member of the
Securities Transfer Agents Medallion Program or other eligible institution
guarantee that the missing items will be received by the depositary within three
NYSE trading days. However, the depositary must
                                        vi
   8

receive the missing items within that three trading day period. See Section 3,
"Procedure for Tendering Shares".

UNTIL WHAT TIME CAN I WITHDRAW TENDERED SHARES?

      You can withdraw tendered Shares at any time until the Offer has expired
and, if we have not agreed to accept your Shares for payment by Friday, July 13,
2001, you can withdraw your tendered Shares at any time after July 13, 2001
until we accept Shares for payment. See Section 4, "Withdrawal Rights".

HOW DO I WITHDRAW TENDERED SHARES?

      To withdraw Shares, you must deliver a written notice of withdrawal, or a
facsimile of one, with the required information to EquiServe, the depositary,
while you have the right to withdraw the Shares.

WHEN AND HOW WILL I BE PAID FOR MY TENDERED SHARES?

      Subject to the terms and conditions of the Offer, we will pay for
16,730,502 Shares tendered and not withdrawn as soon as practicable after the
Expiration Date, subject to the satisfaction or waiver of the conditions to the
Offer, as set forth in Section 14, "Conditions of the Offer". We do, however,
reserve the right, in our sole discretion and subject to applicable law, to
delay payment for Shares in order to comply with applicable law. All Shares not
purchased in the Offer, including as a result of proration, will be returned to
their respective holders.

      In all cases, payment for tendered Shares will be made only after timely
receipt by EquiServe of certificates for such Shares (or of a confirmation of a
book-entry transfer of such shares as described in Section 3, "Procedures for
Accepting the Offer and Tendering Shares"), a properly completed and duly
executed Letter of Transmittal (or an Agent's Message (as defined in Section 3)
in connection with a book-entry transfer) and any other required documents for
such Shares.

      We will pay for 16,730,502 Shares validly tendered and not withdrawn by
depositing the aggregate purchase price for such Shares with EquiServe, the
depositary, which will act as your agent for the purpose of receiving payments
from us and transmitting such payments to you.

      As noted earlier, if more than 16,730,502 Shares are validly tendered and
not withdrawn, we will accept for payment and pay for only 16,730,502 Shares on
a pro rata basis (with appropriate adjustments to avoid purchase of fractional
Shares) based on the number of Shares properly tendered by each stockholder.
Because of the difficulty of determining the precise number of Shares properly
tendered and not withdrawn (due in part to the guaranteed delivery procedures
described in Section 3), Williams does not expect that it will be able to
announce the final results of proration or pay for any Shares until at least
five NYSE trading days after the Expiration Date. Preliminary results of
proration will be announced by press release as promptly as practicable after
the Expiration Date. You may obtain such preliminary information from the
Information Agent and may be able to obtain such information from your broker.

HAVE ANY STOCKHOLDERS OF BARRETT RESOURCES AGREED TO VOTE IN FAVOR OF THE
MERGER?

      No. However, if the Offer is completed, Barrett Resources will hold a
special meeting of its stockholders to vote on the approval of the merger. At
that special meeting, we will vote the Shares purchased by us in the Offer in
favor of the merger and the adoption of the Merger Agreement.

                                       vii
   9

IF 16,730,502 SHARES ARE TENDERED AND ACCEPTED FOR PAYMENT, WHAT WILL HAPPEN TO
BARRETT RESOURCES AFTER THE OFFER?

      The Merger Agreement provides for Barrett Resources to merge with and into
us, unless certain conditions relating to the United States federal income tax
treatment of the Offer and the merger of Barrett Resources with and into us are
not met, in which case Purchaser may, at Williams' reasonable discretion, be
merged with and into Barrett Resources. The merger is dependent on Barrett
Resources stockholders that own at least a majority of the Shares outstanding on
the record date (set to determine those persons entitled to vote on the merger)
voting in favor of the merger. If the Offer is successful, Williams will
beneficially own at least 16,730,502 Shares, which amount of Shares is expected
to constitute approximately 50% of the outstanding Shares, which would
effectively give us the voting power to approve the merger without the
affirmative vote of other stockholders. We have agreed to vote all these Shares
in favor of the merger.

      Therefore, if we acquire 16,730,502 Shares pursuant to the Offer or
otherwise, Barrett Resources and Purchaser will merge. Once the merger takes
place, Barrett Resources will no longer be publicly owned and will instead
become a wholly-owned subsidiary of Williams and Shares of Barrett Resources
will no longer be traded through the NYSE or on any other securities exchange.
See "Introduction" and Section 7, "Possible Effects of the Offer on the Market
for the Shares; NYSE Listing; Exchange Act Registration; Margin Regulations".

IF I DECIDE NOT TO TENDER AND THE OFFER IS COMPLETED, HOW WILL MY SHARES BE
AFFECTED?

      If the Offer is completed and the merger takes place, stockholders not
tendering in the Offer (other than Barrett Resources, Williams, Purchaser, and
any other subsidiary of Williams) will receive, for each Share they hold, 1.767
shares of Williams common stock. Therefore, if the Offer is completed and the
merger takes place, the difference to you between tendering your Shares and not
tendering your Shares is that (i) if you tender you will be paid cash for at
least half (or more, depending on proration) of the Shares that you tender in
the Offer and (ii) if you do not tender you will receive only shares of Williams
common stock in exchange for your Shares that you do not tender in the Offer.

WHAT IS THE MARKET VALUE OF MY SHARES AS OF A RECENT DATE?

      On May 4, 2001, the last full NYSE trading day before we announced the
execution of the Merger Agreement, the closing price of the Shares of Barrett
Resources reported on the NYSE was $67.30 per Share. On May 11, 2001, the last
full trading day before the date of this Offer to Purchase, the closing price of
the Shares reported on the NYSE was $71.08 and on March 6, 2001, the last full
trading day before Shell Oil Company disclosed its unsolicited bid for Barrett
Resources, the closing price of the Shares reported on the NYSE was $45.62. We
advise you to obtain a recent quotation for Shares before deciding whether to
tender your Shares.

WHAT HAPPENED TO THE SHELL OFFER?

      On May 7, 2001, the day Williams and Barrett Resources announced that they
had executed the Merger Agreement, Shell Oil Company and its subsidiary, SRM
Acquisition Company, terminated their offer to acquire Barrett Resources.

WHO CAN I TALK TO IF I HAVE QUESTIONS ABOUT THE OFFER?

      You can call Georgeson Shareholder Communications, Inc., the information
agent for the Offer, at (800) 223-2064 (toll free) or banks and brokers can call
(212) 440-9800 (call collect) or Merrill Lynch & Co., the dealer manager for the
Offer, at (212) 236-3790 (call collect).

                                       viii
   10

To:  All Holders of Shares of Common Stock
     of Barrett Resources Corporation:

                                  INTRODUCTION

      Resources Acquisition Corp. ("Purchaser", "we" or "us"), a wholly-owned
subsidiary of The Williams Companies, Inc. ("Williams"), hereby offers to
purchase a total of 16,730,502 shares of common stock, par value $0.01 per share
(including the associated Barrett Resources Rights (as defined herein), the
"Shares"), of Barrett Resources Corporation ("Barrett Resources") at a purchase
price of $73.00 per Share, net to the seller in cash, without interest (the
"Offer Price"), on the terms and subject to the conditions set forth in this
Offer to Purchase and in the related Letter of Transmittal (which, as amended or
supplemented from time to time, together constitute the "Offer").

      Tendering stockholders whose Shares are registered in their own name and
who tender directly to the Depositary (as described below) will not be required
to pay brokerage fees or commissions or, except as described in Instruction 6 of
the Letter of Transmittal, stock transfer taxes on the sale of Shares in the
Offer. However, if you do not complete and sign the Substitute Form W-9 that is
included in the Letter of Transmittal, you may be subject to a required backup
federal income tax withholding of 31% of the gross proceeds payable to you. See
Section 3. We will pay all charges and expenses of Merrill Lynch & Co. ("Merrill
Lynch"), as dealer manager (the "Dealer Manager"), EquiServe Trust Company,
N.A., as depositary (the "Depositary"), and Georgeson Shareholder
Communications, Inc., as information agent (the "Information Agent"), incurred
in connection with the Offer. See Section 16.

THE BOARD OF DIRECTORS OF BARRETT RESOURCES HAS UNANIMOUSLY APPROVED THE OFFER,
THE MERGER (AS DEFINED HEREIN) AND THE MERGER AGREEMENT (AS DEFINED HEREIN), HAS
DETERMINED THAT THE MERGER AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY,
INCLUDING THE OFFER AND THE MERGER, ARE ADVISABLE AND ARE FAIR TO AND IN THE
BEST INTERESTS OF THE STOCKHOLDERS OF BARRETT RESOURCES AND RECOMMENDS THAT
STOCKHOLDERS OF BARRETT RESOURCES ACCEPT THE OFFER, TENDER THEIR SHARES PURSUANT
TO THE OFFER AND APPROVE AND ADOPT THE MERGER AGREEMENT AND THE MERGER AT THE
TIME OF THE BARRETT RESOURCES SPECIAL MEETING (AS DEFINED HEREIN).

      For a discussion of the Barrett Resources Board's recommendation, see Item
4, "The Solicitation or Recommendation" set forth in Barrett Resources'
Solicitation/Recommendation Statement on Schedule 14D-9 (the "Schedule 14D-9"),
which is being mailed to stockholders with this Offer to Purchase.

      To the extent that more than 16,730,502 Shares are tendered in the Offer,
Purchaser will purchase 16,730,502 Shares in the Offer on a pro rata basis (with
appropriate adjustments to avoid purchase of fractional Shares) based on the
number of Shares properly tendered by each stockholder prior to or on the
Expiration Date (as defined below) and not withdrawn. See Sections 2 and 3.

      We are not required to purchase any Shares unless at least 16,730,502
Shares are validly tendered and not withdrawn prior to the expiration of the
Offer (the "Minimum Condition"). Unless Barrett Resources consents, we may not
waive or reduce the Minimum Condition or elect to purchase all tendered Shares
if the Minimum Condition is not met. See Sections 1, 14 and 15.

THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THE WAITING PERIOD UNDER THE
HART-SCOTT-RODINO ANTITRUST IMPROVEMENTS ACT OF 1976, AS AMENDED, APPLICABLE TO
THE PURCHASE OF SHARES PURSUANT TO THE OFFER HAVING EXPIRED OR BEEN TERMINATED.
THE OFFER IS NOT SUBJECT TO A FINANCING CONDITION. THE OFFER IS ALSO SUBJECT TO
CERTAIN OTHER TERMS AND CONDITIONS SET FORTH IN THIS OFFER TO PURCHASE. SEE
SECTIONS 1, 14 AND 15.
                                        1
   11

      We are making the Offer pursuant to an Agreement and Plan of Merger (the
"Merger Agreement"), dated as of May 7, 2001, by and among Williams, Purchaser
and Barrett Resources. Following the consummation of the Offer and the
satisfaction or waiver of the conditions set forth in the Merger Agreement,
Barrett Resources will merge with and into Purchaser with Purchaser continuing
as the surviving corporation, unless certain conditions related to the United
States federal income tax treatment of the Offer and the merger of Barrett
Resources with and into Purchaser are not satisfied, in which case Purchaser
may, at Williams' reasonable discretion, merge with and into Barrett Resources
with Barrett Resources continuing as the surviving corporation. Whichever merger
shall occur, as described above, is referred to herein as the "Merger". In the
Merger, stockholders of Barrett Resources will have each of their Shares (other
than Shares held by Barrett Resources, Williams, Purchaser or any other
subsidiary of Williams) converted into 1.767 shares of Williams common stock,
par value $1.00 per share (including the associated Williams Rights (as defined
herein), the "Williams Common Stock"), with cash in lieu of fractional shares.
Section 11 contains a more detailed description of the Merger Agreement and the
consideration payable in the Merger in respect of the Shares. Section 5
describes the principal United States federal income tax consequences of the
sale or exchange of Shares in the Offer and the Merger. As used herein,
"Williams Rights" means the Series A Junior Participating Preferred Stock
purchase rights issued pursuant to the Rights Agreement dated as of February 6,
1996, between Williams and First Chicago Trust Company of New York, as amended.

      As noted above, each Share will be converted into 1.767 shares of Williams
Common Stock in the Merger. Based on the closing sale price of the Williams
Common Stock reported on the New York Stock Exchange ("NYSE") on Friday, May 4,
2001, the last full trading day before the date of announcement of the execution
of the Merger Agreement, the 1.767 shares of Williams Common Stock that would be
issued for each Share in the Merger had a value of $73.63. Based on the closing
sale price of Williams Common Stock reported on the NYSE on Friday, May 11,
2001, the last full trading day before the date of this Offer to Purchase, the
1.767 shares of Williams Common Stock that would be issued for each Share in the
Merger had a value of $71.09.

THE MARKET VALUE OF THE SHARES OF WILLIAMS COMMON STOCK THAT BARRETT RESOURCES
STOCKHOLDERS WILL RECEIVE IN THE MERGER WILL VARY AS A RESULT OF THE FIXED
EXCHANGE RATIO AS THE WILLIAMS COMMON STOCK PRICE FLUCTUATES.

      The exchange ratio of 1.767 shares of Williams Common Stock per Barrett
Resources Share is a fixed ratio that will not be adjusted as a result of any
increase or decrease in the market price of either shares of Williams Common
Stock or the Shares. The market price of shares of Williams Common Stock at the
time the Merger is completed may be higher or lower than the price on the date
of the Merger Agreement, the date of this Offer, the date of completion of this
Offer or the date of the Barrett Resources Special Meeting to be held to vote on
the Merger. If the market price of Williams Common Stock decreases before the
Merger, no additional shares of Williams Common Stock will be received by
Barrett Resources' stockholders to make up for the decrease in the market value
of the Williams Common Stock, and accordingly, the market value of the Williams
Common Stock to be received by Barrett Resources' stockholders would decrease.
Various factors may affect the prices of shares of Williams Common Stock,
including:

      - changes in the business, operations, or prospects of Barrett Resources
        or Williams;

      - market assessments of the benefits of the Merger and of the likelihood
        that the Merger will be completed; and

      - general market, industry and economic conditions.

To a large extent, these factors are beyond our control, Williams' control or
the control of Barrett Resources.

                                        2
   12

      Because the Merger will be completed only after the Barrett Resources
Special Meeting, there is no way to be sure that the price of the shares of
Williams Common Stock now, or at the time of the completion of the Offer, will
be indicative of its price on the date the Merger is completed. The market price
of Williams Common Stock may increase and decrease significantly before and
after completion of the Merger. As a result, the $73.00 per Share that a Barrett
Resources stockholder receives in the Offer may be worth more or less than the
shares of Williams Common Stock to be received in the Merger. WE URGE YOU TO
OBTAIN CURRENT MARKET QUOTATIONS FOR BOTH THE SHARES AND THE WILLIAMS COMMON
STOCK BEFORE DECIDING WHETHER TO TENDER YOUR SHARES IN THE OFFER.

THE OFFER DOES NOT CONSTITUTE A SOLICITATION OF PROXIES FOR ANY MEETING OF THE
STOCKHOLDERS OF BARRETT RESOURCES OR ANY OFFER TO SELL OR SOLICITATION OF OFFERS
TO BUY WILLIAMS COMMON STOCK OR OTHER SECURITIES. ANY SUCH SOLICITATION WILL BE
MADE ONLY PURSUANT TO SEPARATE PROXY MATERIALS PURSUANT TO THE REQUIREMENTS OF
SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED (THE "EXCHANGE
ACT"), AND ANY SUCH OFFER WILL BE MADE ONLY THROUGH A REGISTRATION STATEMENT AND
PROSPECTUS PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT"), WHICH PROSPECTUS WILL ALSO CONSTITUTE A PROXY
STATEMENT FOR THE BARRETT RESOURCES SPECIAL MEETING OF STOCKHOLDERS TO BE HELD
TO VOTE UPON THE MERGER AND THE MERGER AGREEMENT.

      Goldman, Sachs & Co. ("Goldman Sachs") and Petrie Parkman & Co., Inc.
("Petrie Parkman"), Barrett Resources' financial advisors, each delivered to the
Board of Directors of Barrett Resources its written opinion, dated May 7, 2001,
that as of that date and on the basis of and subject to the matters described in
such opinion, the consideration to be received by holders of Shares in the Offer
and the Merger, taken together, was fair from a financial point of view to such
holders. Copies of the Goldman Sachs and Petrie Parkman opinions are included
with Barrett Resources' Solicitation/Recommendation Statement on Schedule 14D-9,
which is being mailed with this Offer to Purchase. Stockholders are urged to
read both opinions in their entirety, each of which sets forth the procedures
followed, matters reviewed and assumptions made by Goldman Sachs and Petrie
Parkman in preparing their respective opinions.

      The consummation of the Merger is subject to the satisfaction of certain
conditions, including the approval and adoption of the Merger Agreement and the
Merger by the affirmative vote of a majority of the outstanding Shares (the
"Barrett Resources Stockholder Approval"). Barrett Resources has agreed to
convene a special meeting of its stockholders for such purpose (the "Barrett
Resources Special Meeting") as promptly as practicable after the consummation of
the Offer and after the registration statement for the Williams Common Stock to
be exchanged for Shares pursuant to the Merger becomes effective. If Purchaser
acquires (pursuant to the Offer or otherwise) approximately 50% of the
outstanding Shares (which is expected to occur if the Minimum Condition is met),
Purchaser will effectively have sufficient voting power to approve and adopt the
Merger Agreement and the Merger without the vote of other stockholders of
Barrett Resources.

      The Merger Agreement provides that, promptly upon the purchase of Shares
by Purchaser pursuant to the Offer, we will be entitled to designate a number of
directors to the Barrett Resources Board, rounded up to the next whole number,
which equals the product obtained by multiplying the total number of directors
on Barrett Resources' Board (giving effect to the directors designated by us
pursuant to the provisions of the Merger Agreement) by the percentage that the
number of Shares accepted for payment pursuant to the Offer bears to the total
number of Shares then outstanding. In the Merger Agreement, Barrett Resources
has agreed to increase the size of its Board or exercise its best efforts to
secure the resignations of incumbent directors or both as is necessary to enable
Williams' designees to be elected to the Barrett Resources Board. Following the
Offer, it is anticipated that representatives of Williams will constitute at
least one-half of the members of the Barrett Resources Board of Directors.

                                        3
   13

      Barrett Resources has informed us that, as of May 3, 2001, there were (a)
33,461,004 Shares issued and outstanding and (b) 2,302,073 Shares subject to
issuance under outstanding options.

      Pursuant to the Merger Agreement, Barrett Resources has amended the Rights
Agreement, dated as of August 5, 1997, as amended (the "Barrett Resources Rights
Agreement"), between Barrett Resources and Fleet National Bank, as successor to
BankBoston, N.A., as Rights Agent, in accordance with the terms of the Barrett
Resources Rights Agreement to provide that neither Williams nor Purchaser,
individually or collectively, shall be deemed an "Acquiring Person" and no
"Distribution Date" (as such terms are defined in the Barrett Resources Rights
Agreement) shall be deemed to occur solely as a result of (i) the announcement,
approval, execution or delivery of the Merger Agreement, (ii) the consummation
of the Offer and/or the Merger or (iii) the consummation of the other
transactions contemplated by the Merger Agreement. As used herein, the term
"Barrett Resources Rights" means the Series A Junior Participating Preferred
Stock purchase rights issued pursuant to the Barrett Resources Rights Agreement.

THE OFFER IS CONDITIONED UPON THE FULFILLMENT OF ALL OF THE CONDITIONS DESCRIBED
IN SECTION 14 BELOW. THE OFFER WILL EXPIRE AT 12:00 MIDNIGHT, EASTERN TIME, ON
MONDAY, JUNE 11, 2001, UNLESS WE EXTEND IT.

THIS OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN IMPORTANT
INFORMATION WHICH YOU SHOULD READ CAREFULLY BEFORE YOU MAKE ANY DECISION WITH
RESPECT TO THE OFFER.

1. TERMS OF THE OFFER.

      Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of any extension or
amendment), we will purchase 16,730,502 Shares validly tendered and not
withdrawn in accordance with the procedures set forth in Section 4 of this Offer
to Purchase on or prior to the Expiration Date. To the extent more than
16,730,502 Shares are validly tendered and not withdrawn in the Offer, we will
purchase 16,730,502 Shares in the Offer on a pro rata basis (with appropriate
adjustments to avoid the purchase of fractional Shares) based on the number of
Shares properly tendered and not withdrawn by each stockholder prior to or on
the Expiration Date. In the event that proration of tendered Shares is required,
because of the difficulty of determining the precise number of Shares properly
tendered and not withdrawn (due in part to the guaranteed delivery procedure
described under Section 3), Purchaser does not expect that it will be able to
announce the final results of such proration or pay for any Shares until at
least five NYSE trading days after the Expiration Date. Preliminary results of
the proration will be announced by a press release as promptly as practicable
after the Expiration Date. Stockholders may obtain preliminary proration
information from the Information Agent and may also be able to obtain such
proration information from their brokers. Tendering stockholders will not
receive payment for Shares accepted for payment pursuant to the Offer, or Share
certificates for Shares returned as a result of proration or otherwise, until
the final proration factor is known. Because we are only offering to purchase a
fixed number of Shares in the Offer, there will be no subsequent offering
period.

      Williams and Purchaser have agreed with Barrett Resources that we will not
terminate the Offer between scheduled Expiration Dates and that, in the event
that we would otherwise be entitled to terminate the Offer at any scheduled
Expiration Date due to the failure of one or more of the conditions to the
Offer, unless the Merger Agreement shall have been terminated pursuant to its
terms, Purchaser will, and Williams will cause Purchaser to, extend the Offer
for such period or periods as may be determined by Purchaser until such date as
the conditions to the Offer have been satisfied or such later date as required
by applicable law; provided, however, that Purchaser will not be required to
extend the Offer beyond August 31, 2001. Each of Williams and Barrett Resources
may also terminate the Merger Agreement if any or all of such conditions are not
satisfied on or before August 31, 2001, unless the failure to consummate the
Offer is the result of a willful and material breach of the Merger Agreement by
the party seeking to terminate the Merger Agreement. We may also extend the
Offer for any period required

                                        4
   14

by applicable rules, regulations, interpretations or positions of the Securities
and Exchange Commission ("SEC") or its staff applicable to the Offer or for any
period required by applicable law. If we extend the Offer under any
circumstances, the term "Expiration Date" will mean the time and date on which
the Offer, as so extended, will expire.

      If at the Expiration Date any or all the conditions to the Offer described
in Section 14 have not been satisfied or waived, then, subject to the provisions
of the Merger Agreement, unless the Merger Agreement is terminated, we will
extend the Expiration Date for an additional period or periods of time, by
giving oral or written notice of the extension to the Depositary. However, there
can be no assurance that we will exercise our right to extend the Offer (other
than as may be required by the Merger Agreement or by applicable law). During
any such extension, all Shares previously tendered and not withdrawn will remain
subject to the Offer and subject to your right to withdraw Shares previously
tendered. See Section 4.

      Subject to the applicable regulations of the SEC and the terms of the
Merger Agreement, we also reserve the right, in our sole discretion, at any time
or from time to time, to: (a) delay purchase of, or payment for, any Shares
pending receipt of any regulatory or governmental approvals specified in Section
15; (b) terminate the Offer if any condition referred to in Section 14 has not
been satisfied or upon the occurrence of any event specified in Section 14; and
(c) except as set forth in the Merger Agreement, waive any condition or
otherwise amend the Offer in any respect, in each case, by giving oral or
written notice of the delay, termination, waiver or amendment to the Depositary
by making a public announcement thereof. We acknowledge (i) that Rule 14e-1(c)
under the Exchange Act requires us to pay the consideration offered or return
the Shares tendered promptly after the termination or withdrawal of the Offer
and (ii) that we may not delay purchase of, or payment for, any Shares upon the
occurrence of any event specified in Section 14 without extending the period of
time during which the Offer is open.

      The rights we reserve in the preceding paragraph are in addition to our
rights described in Section 14. Any extension, delay, termination or amendment
of the Offer will be followed as promptly as practicable by a public
announcement. An announcement in the case of an extension will be made no later
than 9:00 a.m., eastern time, on the next business day after the previously
scheduled Expiration Date. Without limiting the manner in which we may choose to
make any public announcement, subject to applicable law (including Rules
14d-4(d) and 14d-6(c) under the Exchange Act, which require that material
changes be promptly disseminated to holders of Shares), we will have no
obligation to publish, advertise or otherwise communicate any such public
announcement other than by issuing a release to the Dow Jones News Service.

      In the Merger Agreement, we have agreed that, without the prior written
consent of Barrett Resources, we will not (a) decrease the Offer Price or change
the form of consideration payable in the Offer; (b) seek to purchase fewer than
16,730,502 Shares; (c) impose additional conditions to the Offer; or (d) amend
any other term or condition of the Offer in any manner materially adverse to the
holders of Shares.

      If we make a material change in the terms of the Offer or if we waive a
material condition to the Offer, we will extend the Offer and disseminate
additional tender offer materials to the extent required by Rules 14d-4(d),
14d-6(c) and 14e-1 under the Exchange Act. The minimum period during which a
tender offer must remain open following material changes in the terms of the
Offer, other than a change in price or a change in percentage of securities
sought, depends upon the facts and circumstances, including the materiality of
the changes. In the SEC's view, an offer should remain open for a minimum of
five business days from the date the material change is first published, sent or
given to stockholders, and, if material changes are made with respect to
information that approaches the significance of price and the percentage of
securities sought, a minimum of ten business days may be required to allow for
adequate dissemination and investor response. With respect to a change in price,
a minimum of ten business days from the date of the change is generally required
to allow for adequate dissemination to stockholders. Accordingly, if, prior to
the Expiration Date, we increase or decrease the number of Shares being sought,
or increase or decrease the consideration offered pursuant to the Offer, and if
the Offer is scheduled to

                                        5
   15

expire at any time earlier than the period ending on the tenth business day from
the date that notice of the increase or decrease is first published, sent or
given to holders of Shares, we will extend the Offer at least until the
expiration of such period of ten business days. For purposes of the Offer, a
"business day" means any day other than a Saturday, Sunday or a federal holiday
and consists of the time period from 12:01 a.m. through 12:00 midnight, eastern
time.

      The Offer is conditioned upon, among other things, the satisfaction of the
Minimum Condition. Consummation of the Offer is also conditioned upon expiration
or termination of all waiting periods imposed by the Hart-Scott-Rodino Antitrust
Improvements Act of 1976, as amended, and the regulations thereunder (the "HSR
Act"), and the other conditions set forth in Section 14. Subject to the terms of
the Merger Agreement, we reserve the right (but are not obligated), in
accordance with applicable rules and regulations of the SEC, to waive any or all
of those conditions. If, by the Expiration Date, any or all of those conditions
have not been satisfied, we may, without the consent of Barrett Resources, elect
to (a) extend the Offer and, subject to applicable withdrawal rights, retain all
tendered Shares until the expiration of the Offer, as extended, subject to the
terms of the Offer and the Merger Agreement; (b) waive all of the unsatisfied
conditions, subject to the terms of the Offer and the Merger Agreement and,
subject to complying with the applicable rules and regulations of the SEC, and
accept for payment the 16,730,502 Shares so tendered; or (c) subject to our
obligations to extend the Offer until August 31, 2001 unless the Merger
Agreement has been terminated in accordance with its terms, terminate the Offer
and not accept for payment any Shares and return all tendered Shares to
tendering stockholders. See Section 11. In the event that we waive any condition
set forth in Section 14, the SEC may, if the waiver is deemed to constitute a
material change to the information previously provided to the stockholders,
require that the Offer remain open for an additional period of time and/or that
we disseminate information concerning such waiver.

      Barrett Resources has provided us with its stockholder lists and security
position listings for the purpose of disseminating the Offer to holders of
Shares. We will mail this Offer to Purchase, the related Letter of Transmittal
and other relevant materials to record holders of Shares and we will furnish the
materials to brokers, dealers, commercial banks, trust companies and similar
persons whose names, or the names of whose nominees, appear on the
securityholder lists or, if applicable, who are listed as participants in a
clearing agency's security position listing, for forwarding to beneficial owners
of Shares.

2. ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES; PRORATION.

      Upon the terms and subject to the conditions of the Offer (including, if
we extend or amend the Offer, the terms and conditions of the Offer as so
extended or amended), we will purchase, by accepting for payment, and will pay
for 16,730,502 Shares validly tendered and not withdrawn (as permitted by
Section 4) prior to the Expiration Date promptly after the later of (a) the
Expiration Date and (b) the satisfaction or waiver of all the conditions to the
Offer set forth in Section 14. In addition, subject to applicable rules of the
SEC, we reserve the right to delay acceptance for payment of or payment for
Shares pending receipt of any regulatory or governmental approvals specified in
Section 15. For information with respect to regulatory approvals that we are
required to obtain prior to the completion of the Offer, see Section 15.

      In all cases, we will pay for Shares purchased in the Offer only after
timely receipt by the Depositary of (a) certificates representing the Shares
("Share Certificates") or timely confirmation (a "Book-Entry Confirmation") of
the book-entry transfer of the Shares into the Depositary's account at The
Depository Trust Company (the "Book-Entry Transfer Facility") pursuant to the
procedures set forth in Section 3; (b) the Letter of Transmittal (or a
facsimile), properly completed and duly executed, with any required signature
guarantees or an Agent's Message (as defined herein) in connection with a
book-entry transfer; and (c) any other documents that the Letter of Transmittal
requires.

      The term "Agent's Message" means a message transmitted by the Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of a
Book-Entry Confirmation, which states that the Book-Entry Transfer Facility has
received an express acknowledgment from the participant in the Book-

                                        6
   16

Entry Transfer Facility tendering the Shares which are the subject of the
Book-Entry Confirmation that the participant has received and agrees to be bound
by the terms of the Letter of Transmittal and that we may enforce that agreement
against the participant.

      For purposes of the Offer, we will be deemed to have accepted for payment,
and purchased, Shares validly tendered and not withdrawn if and when we give
oral or written notice to the Depositary of our acceptance of the Shares for
payment pursuant to the Offer. In all cases, upon the terms and subject to the
conditions of the Offer, payment for Shares purchased pursuant to the Offer will
be made by deposit of the aggregate purchase price for the Shares with the
Depositary, which will act as agent for tendering stockholders for the purpose
of receiving payment from us and transmitting payment to validly tendering
stockholders.

UNDER NO CIRCUMSTANCES WILL WE PAY INTEREST ON THE PURCHASE PRICE FOR SHARES,
REGARDLESS OF ANY EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH PAYMENT.

      If we do not purchase any tendered Shares pursuant to the Offer for any
reason, including proration, or if you submit Share Certificates representing
more Shares than you wish to tender, we will return Share Certificates
representing unpurchased or untendered Shares, without expense to you (or, in
the case of Shares delivered by book-entry transfer into the Depositary's
account at the Book-Entry Transfer Facility pursuant to the procedures set forth
in Section 3, the Shares will be credited to an account maintained within the
Book-Entry Transfer Facility), as promptly as practicable following the
expiration, termination or withdrawal of the Offer.

IF, PRIOR TO THE EXPIRATION DATE, WE INCREASE THE PRICE OFFERED TO HOLDERS OF
SHARES IN THE OFFER, WE WILL PAY THE INCREASED PRICE TO ALL HOLDERS OF SHARES
THAT WE PURCHASE IN THE OFFER, WHETHER OR NOT THE SHARES WERE TENDERED BEFORE
THE INCREASE IN PRICE.

      We reserve the right, subject to the provisions of the Merger Agreement,
to transfer or assign, in whole or from time to time in part, to one or more of
Williams' wholly-owned subsidiaries the right to purchase all or any portion of
the Shares tendered in the Offer, but any such transfer or assignment will not
relieve us of our obligations under the Offer or prejudice your rights to
receive payment for Shares validly tendered and accepted for payment in the
Offer.

      If more than 16,730,502 Shares are validly tendered prior to the
Expiration Date and are not properly withdrawn, we will, upon the terms and
subject to the conditions of the Offer, accept for payment and pay for only
16,730,502 Shares, on a pro rata basis, with adjustments to avoid purchases of
fractional Shares, based upon the number of Shares validly tendered prior to the
Expiration Date and not properly withdrawn. Because of the difficulty of
determining precisely the number of Shares validly tendered and not withdrawn,
Purchaser would not expect to be able to announce the final results of proration
or pay for Shares until at least five NYSE trading days after the Expiration
Date. Preliminary results of proration will be announced by press release as
promptly as practicable after the Expiration Date. Holders of Shares may obtain
such preliminary information from the Information Agent and may also be able to
obtain such preliminary information from their brokers.

3. PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES.

      VALID TENDER OF SHARES.  Except as set forth below, in order for you to
tender Shares in the Offer, the Depositary must receive the Letter of
Transmittal (or a facsimile), properly completed and signed, together with any
required signature guarantees, or an Agent's Message in connection with a
book-entry delivery of Shares, and any other documents that the Letter of
Transmittal requires at one of the Depositary's addresses set forth on the back
cover of this Offer to Purchase on or prior to the Expiration Date and either
(a) you must deliver Share Certificates representing tendered Shares to the
Depositary or you must cause your Shares to be tendered pursuant to the
procedure for book-entry transfer set forth

                                        7
   17

below and the Depositary must receive Book-Entry Confirmation, in each case on
or prior to the Expiration Date, or (b) you must comply with the guaranteed
delivery procedures set forth below.

THE METHOD OF DELIVERY OF SHARE CERTIFICATES, THE LETTER OF TRANSMITTAL AND ALL
OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER
FACILITY, IS AT YOUR OPTION AND SOLE RISK, AND DELIVERY WILL BE CONSIDERED MADE
ONLY WHEN THE DEPOSITARY ACTUALLY RECEIVES THE SHARE CERTIFICATES OR
CONFIRMATION OF A BOOK-ENTRY TRANSFER OF THE SHARES TENDERED. IF DELIVERY IS BY
MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS
RECOMMENDED. IN ALL CASES, YOU SHOULD ALLOW SUFFICIENT TIME TO ENSURE TIMELY
DELIVERY.

      BOOK-ENTRY TRANSFER.  The Depositary will establish an account with
respect to the Shares at the Book-Entry Transfer Facility for purposes of the
Offer within two business days after the date of this Offer to Purchase. Any
financial institution that is a participant in the system of the Book-Entry
Transfer Facility may make book-entry delivery of Shares by causing the
Book-Entry Transfer Facility to transfer the Shares into the Depositary's
account at the Book-Entry Transfer Facility in accordance with the Book-Entry
Transfer Facility's procedures. However, although Shares may be delivered
through book-entry transfer into the Depositary's account at the Book-Entry
Transfer Facility, the Depositary must receive the Letter of Transmittal (or
facsimile), properly completed and signed, with any required signature
guarantees, or an Agent's Message, and any other required documents, at one of
its addresses set forth on the back cover of this Offer to Purchase on or before
the Expiration Date, or you must comply with the guaranteed delivery procedure
set forth below.

DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN ACCORDANCE WITH THE
BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO THE
DEPOSITARY.

      SIGNATURE GUARANTEES.  A bank, broker, dealer, credit union, savings
association or other entity which is a member in good standing of the Securities
Transfer Agents Medallion Program (an "Eligible Institution") must guarantee
signatures on all Letters of Transmittal, unless the Shares tendered are
tendered (a) by a registered holder of Shares who has not completed either the
box labeled "Special Payment Instructions" or the box labeled "Special Delivery
Instructions" on the Letter of Transmittal or (b) for the account of an Eligible
Institution. See Instruction 1 of the Letter of Transmittal.

      If the Share Certificates are registered in the name of a person other
than the signer of the Letter of Transmittal, or if payment is to be made to, or
Share Certificates for unpurchased Shares are to be issued or returned to, a
person other than the registered holder, then the tendered certificates must be
endorsed or accompanied by appropriate stock powers, signed exactly as the name
or names of the registered holder or holders appear on the Share Certificates,
with the signatures on the Share Certificates or stock powers guaranteed by an
Eligible Institution as provided in the Letter of Transmittal. See Instructions
1 and 5 of the Letter of Transmittal.

      If the Share Certificates are forwarded separately to the Depositary, a
properly completed and duly executed Letter of Transmittal (or facsimile) must
accompany each delivery of Share Certificates.

      GUARANTEED DELIVERY.  If you want to tender Shares in the Offer and your
Share Certificates are not immediately available or time will not permit all
required documents to reach the Depositary on or before the Expiration Date or
the procedures for book-entry transfer cannot be completed on time, your

                                        8
   18

Shares may nevertheless be tendered if you comply with all of the following
guaranteed delivery procedures:

      (1) your tender must be made by or through an Eligible Institution;

      (2) the Depositary must receive, as described below, a properly completed
          and signed Notice of Guaranteed Delivery, substantially in the form
          made available by us, on or before the Expiration Date; and

      (3) the Depositary must receive the Share Certificates (or a Book-Entry
          Confirmation of transfer of the Shares tendered) representing all
          tendered Shares, in proper form for transfer together with a properly
          completed and duly executed Letter of Transmittal (or facsimile), with
          any required signature guarantees (or, in the case of a book-entry
          transfer, an Agent's Message) and any other documents required by the
          Letter of Transmittal within three trading days after the date of
          execution of the Notice of Guaranteed Delivery. A "trading day" is any
          day on which the NYSE is open for business.

      You may deliver the Notice of Guaranteed Delivery by hand, mail or
facsimile transmission to the Depositary. The Notice of Guaranteed Delivery must
include a guarantee by an Eligible Institution in the form set forth in the
Notice of Guaranteed Delivery.

      Notwithstanding any other provision of the Offer, we will pay for Shares
only after timely receipt by the Depositary of Share Certificates for, or of
Book-Entry Confirmation with respect to, the Shares tendered, a properly
completed and duly executed Letter of Transmittal (or facsimile thereof)
together with any required signature guarantees (or, in the case of a book-entry
transfer, an Agent's Message) and any other documents required by the Letter of
Transmittal. Accordingly, payment might not be made to all tendering
stockholders at the same time, and will depend upon when the Depositary receives
Share Certificates or Book-Entry Confirmation that the Shares have been
transferred into the Depositary's account at the Book-Entry Transfer Facility.

      BACKUP FEDERAL INCOME TAX WITHHOLDING.  Under the backup federal income
tax withholding laws applicable to certain stockholders (other than certain
exempt stockholders, including, among others, all corporations and certain
foreign individuals), the Depositary may be required to withhold 31% of the
amount of any payments made to those stockholders pursuant to the Offer. To
prevent backup federal income tax withholding, you must provide the Depositary
with your correct taxpayer identification number and certify that you are not
subject to backup federal income tax withholding by completing the Substitute
Form W-9 included in the Letter of Transmittal (or, if you are a foreign
stockholder, an appropriate Form W-8). See Instruction 11 of the Letter of
Transmittal.

      TENDERING STOCKHOLDER'S REPRESENTATION AND WARRANTY; PURCHASER'S
ACCEPTANCE CONSTITUTES AN AGREEMENT.  A tender of Shares pursuant to any of the
procedures described above will constitute the tendering stockholder's
acceptance of the terms and conditions of the Offer, as well as the tendering
stockholder's representation and warranty to Purchaser that (a) such stockholder
has a net long position in the Shares being tendered within the meaning of Rule
14e-4 promulgated by the SEC under the Exchange Act and (b) the tender of such
Shares complies with Rule 14e-4. It is a violation of Rule 14e-4 for a person
acting alone or in concert with others, directly or indirectly, to tender Shares
for such person's own account unless at the time of tender and at the Expiration
Date such person has a "net long position" equal to or greater than the amount
tendered in (i) Shares and will deliver or cause to be delivered such Shares for
the purpose of tendering to Purchaser within the period specified in the Offer,
or (ii) other securities immediately convertible into, exercisable for or
exchangeable into Shares ("Equivalent Securities") and, upon the acceptance of
such tender, will acquire such Shares by conversion, exchange or exercise of
such Equivalent Securities to the extent required by the terms of the Offer and
will deliver or cause to be delivered such Shares so acquired for the purpose of
tender to Purchaser within the period specified in the Offer. Rule 14e-4
provides a similar restriction applicable to the tender or guarantee of a tender
on behalf of another person. Purchaser's acceptance for payment of Shares
tendered pursuant to the

                                        9
   19

Offer will constitute a binding agreement between the tendering stockholder and
Purchaser upon the terms and subject to the conditions of the Offer.

      APPOINTMENT AS PROXY.  By executing the Letter of Transmittal (including
through delivery of an Agent's Message), you irrevocably appoint our designees,
and each of them, as your agents, attorneys-in-fact and proxies, with full power
of substitution, in the manner set forth in the Letter of Transmittal, to the
full extent of your rights with respect to the Shares that you tender and that
we accept for payment and with respect to any and all other Shares and other
securities or rights issued or issuable in respect of those Shares on or after
the date of this Offer to Purchase. All such powers of attorney and proxies will
be considered irrevocable and coupled with an interest in the tendered Shares.
This appointment will be effective when we accept your Shares for payment in
accordance with the terms of the Offer. Upon such acceptance for payment, all
other powers of attorney and proxies given by you with respect to your Shares
and such other securities or rights prior to such payment will be revoked,
without further action, and no subsequent powers of attorney and proxies may be
given by you (and, if given, will not be deemed effective). Our designees will,
with respect to the Shares and such other securities and rights for which the
appointment is effective, be empowered to exercise all your voting and other
rights as they in their sole discretion may deem proper at any annual or special
meeting of Barrett Resources' stockholders, or any adjournment or postponement
thereof, or by consent in lieu of any such meeting or otherwise. In order for
Shares to be deemed validly tendered, immediately upon the acceptance for
payment of such Shares, we or our designees must be able to exercise full
voting, consent and other rights with respect to such Shares and other
securities, including voting at any meeting of stockholders.

      DETERMINATION OF VALIDITY.  All questions as to the form of documents and
the validity, eligibility (including time of receipt) and acceptance for payment
of any tender of Shares will be determined by us, in our sole discretion, which
determination will be final and binding on all parties. We reserve the absolute
right to reject any or all tenders determined by us not to be in proper form or
the acceptance of or payment for which may, in the opinion of our counsel, be
unlawful. Subject to the terms of the Merger Agreement and applicable law, we
also reserve the absolute right to waive any of the conditions of the Offer or
any defect or irregularity in any tender of Shares of any particular stockholder
whether or not similar defects or irregularities are waived in the case of other
stockholders.

      Our interpretation of the terms and conditions of the Offer will be final
and binding. No tender of Shares will be deemed to have been validly made until
all defects and irregularities with respect to the tender have been cured or
waived by us. None of Barrett Resources, Williams, Purchaser or any of their
affiliates or assigns, the Dealer Manager, the Depositary, the Information Agent
or any other person or entity will be under any duty to give any notification of
any defects or irregularities in tenders or incur any liability for failure to
give any such notification.

      BINDING AGREEMENT.  Our acceptance for payment of Shares tendered pursuant
to any of the procedures described above will constitute a binding agreement
between us and you upon the terms and subject to the conditions of the Offer.

      If you have any questions about the procedure for tendering Shares or need
additional copies of the Offer to Purchase, the Letter of Transmittal or other
documents, please telephone the Information Agent at (800) 223-2064 (banks and
brokers can call (212) 440-9800, collect).

4. WITHDRAWAL RIGHTS.

      Except as described in this Section 4, tenders of Shares made in the Offer
are irrevocable. You may withdraw Shares that you have previously tendered in
the Offer at any time on or before the Expiration Date only as described in this
Section 4.

      If, for any reason, acceptance for payment of any Shares tendered in the
Offer is delayed, or we are unable to accept for payment or pay for Shares
tendered in the Offer, then, without prejudice to our rights set forth in this
document, the Depositary may, nevertheless, on our behalf, retain Shares that
you have tendered, and you may not withdraw your Shares except to the extent
that you are entitled to and duly

                                        10
   20

exercise withdrawal rights as described in this Section 4. Any such delay will
be by an extension of the Offer to the extent required by applicable law.

      In order for your withdrawal to be effective, you must deliver a written
or facsimile transmission notice of withdrawal to the Depositary at one of its
addresses set forth on the back cover of this Offer to Purchase. Any such notice
of withdrawal must specify your name, the number of Shares that you want to
withdraw, and (if Share Certificates have been tendered) the name of the
registered holder of the Shares as shown on the Share Certificate, if different
from your name. If Share Certificates have been delivered or otherwise
identified to the Depositary, then prior to the physical release of such Share
Certificates, you must submit the serial numbers shown on the particular Share
Certificates evidencing the Shares to be withdrawn and an Eligible Institution
must guarantee the signature on the notice of withdrawal, except in the case of
Shares tendered for the account of an Eligible Institution. If Shares have been
tendered pursuant to the procedures for book-entry transfer set forth in Section
3, the notice of withdrawal must also specify the name and number of the account
at the Book-Entry Transfer Facility to be credited with the withdrawn Shares, in
which case a notice of withdrawal will be effective if delivered to the
Depositary by any method of delivery described in the first sentence of this
paragraph. You may not rescind a withdrawal of Shares. Any Shares that you
withdraw will be considered not validly tendered for purposes of the Offer;
however, you may tender your Shares again at any time before the Expiration Date
by following any of the procedures described in Section 3 of this document.

      All questions as to the form and validity (including time of receipt) of
notices of withdrawal will be determined by us, in our sole discretion, which
determination will be final and binding. None of Barrett Resources, Williams,
Purchaser or any of their affiliates or assigns, the Dealer Manager, the
Depositary, the Information Agent or any other person or entity will be under
any duty to give any notification of any defects or irregularities in any notice
of withdrawal or incur any liability for failure to give any such notification.

5. MATERIAL UNITED STATES FEDERAL INCOME TAX CONSEQUENCES.

      The following is a summary of the material United States federal income
tax consequences of the Offer and the Merger. This discussion is based upon the
Internal Revenue Code of 1986, as amended (the "Code"), Treasury Regulations,
judicial authorities, published positions of the Internal Revenue Service
("IRS") and other applicable authorities, all as in effect on the date hereof
and all of which are subject to change or differing interpretations (possibly
with retroactive effect). This discussion is limited to United States persons
that hold their Shares as capital assets for United States federal income tax
purposes (generally, assets held for investment). This discussion does not
address all of the tax consequences that may be relevant to a particular holder
of Shares or to a holder of Shares that is subject to special treatment under
United States federal income tax laws. If a holder of Shares has differing tax
bases and/or holding periods in respect of its Shares, it should consult its own
tax advisor prior to tendering in the Offer or voting on the Merger about
possibly identifying the particular Shares to be tendered pursuant to the Offer
and exchanged in the Merger and the tax bases and/or holding periods of the
particular Williams Common Stock that it receives pursuant to the Merger. No
ruling has been or will be sought from the IRS regarding any matter discussed
herein. No assurance can be given that the IRS would not assert, or that a court
would not sustain, a position contrary to any of the tax aspects set forth
below. HOLDERS OF SHARES MUST CONSULT THEIR OWN TAX ADVISORS AS TO THE UNITED
STATES FEDERAL INCOME TAX CONSEQUENCES OF THE OFFER AND THE MERGER, AS WELL AS
THE EFFECTS OF STATE, LOCAL AND NON-UNITED STATES TAX LAWS.

      Purchaser expects that the Offer and the Merger will be treated as a
single integrated transaction for United States federal income tax purposes. If
the Offer and the Merger are so treated and assuming that the Merger is effected
as a merger of Barrett Resources with and into Purchaser ("Forward Merger"),
then the Offer and the Forward Merger will be treated as a "reorganization"
within the

                                        11
   21

meaning of Section 368(a) of the Code. As such a "reorganization", the United
States federal income tax consequences of the Offer and the Forward Merger can
be generally summarized as follows:

             Exchange of Shares Solely for Cash.  A holder of Shares that
      tenders all of its Shares and has all of its Shares accepted for tender in
      the Offer will recognize capital gain or loss in an amount equal to the
      difference between the amount of cash received pursuant to the Offer and
      the holder's tax basis in such Shares. The capital gain or loss will be
      long-term capital gain or loss if the holder has held the Shares sold
      pursuant to the Offer for more than one year at the time such Shares are
      sold in the Offer.

             Exchange of Shares Solely for Williams Common Stock.  A holder of
      Shares that exchanges all of its Shares for Williams Common Stock pursuant
      to the Forward Merger will not recognize any gain or loss except with
      respect to cash received in lieu of a fractional share of Williams Common
      Stock (as described below).

             Exchange of Shares for Cash and Williams Common Stock.  A holder of
      Shares that has some of its Shares accepted for tender in the Offer and
      exchanges some of its Shares for Williams Common Stock pursuant to the
      Forward Merger will recognize gain (but not loss) in an amount equal to
      the lesser of (i) the amount of cash received pursuant to the Offer and
      (ii) an amount equal to the excess, if any, of (a) the sum of the amount
      of cash received pursuant to the Offer and the fair market value of the
      Williams Common Stock received pursuant to the Forward Merger over (b) the
      holder's tax basis in its Shares. The gain recognized will be capital gain
      unless the receipt of cash by the holder has the effect of a distribution
      of a dividend, in which case such gain will be treated as ordinary
      dividend income to the extent of the holder's ratable share of accumulated
      earnings and profits as calculated for United States federal income tax
      purposes. For purposes of determining whether the receipt of cash by the
      holder has the effect of the distribution of a dividend, a holder will be
      treated as if the holder first exchanged all of its Shares solely for
      Williams Common Stock and then Williams immediately redeemed a portion of
      such stock for the cash that such holder actually received pursuant to the
      Offer. The IRS has indicated in rulings that any reduction in the interest
      of a minority stockholder that owns a small number of shares in a publicly
      and widely held corporation and that exercises no control over corporate
      affairs would receive capital gain (as opposed to dividend) treatment. In
      determining whether the receipt of cash has the effect of a distribution
      of a dividend, certain constructive ownership rules must be taken into
      account. Holders that exchange Shares for cash pursuant to the Offer and
      Williams Common Stock pursuant to the Forward Merger must consult their
      own tax advisors as to the character of any gain recognized.

             Tax Basis for Williams Common Stock.  A holder of Shares will have
      an aggregate tax basis in Williams Common Stock received pursuant to the
      Forward Merger equal to the holder's aggregate tax basis in its Shares
      surrendered pursuant to the Offer and the Forward Merger, (i) reduced by
      (a) the portion of the holder's tax basis in its Shares surrendered in the
      Forward Merger that is allocable to a fractional share of Williams Common
      Stock for which cash is received and (b) the amount of cash, if any,
      received by the holder pursuant to the Offer, and (ii) increased by the
      amount of gain (including any portion of such gain that is treated as a
      dividend as described above), if any, recognized by the holder in the
      Offer (but not by gain recognized upon the receipt of cash in lieu of a
      fractional share of Williams Common Stock pursuant to the Forward Merger).

             Holding Period for Williams Common Stock.  The holding period for
      Williams Common Stock received by a holder of Shares pursuant to the
      Forward Merger will include the holding period for the Shares surrendered
      in the Offer and the Forward Merger.

             Cash Received in Lieu of a Fractional Share of Williams Common
      Stock.  If a holder of Shares receives cash in lieu of a fractional share
      of Williams Common Stock in the Forward Merger, the holder will generally
      recognize capital gain or loss equal to the difference between the amount
      of cash received in lieu of the fractional share and the portion of the
      holder's tax basis in its Shares surrendered in the Forward Merger that is
      allocable to the fractional share. The capital
                                        12
   22

      gain or loss will be long-term capital gain or loss if the holder's
      holding period for the portion of the Shares deemed exchanged for the
      fractional share is more than one year at the Effective Time (as defined
      in the Merger Agreement) of the Forward Merger.

             Treatment of the Entities.  No gain or loss will be recognized by
      Williams, Purchaser or Barrett Resources as a result of the Offer or the
      Merger.

      Under the Merger Agreement, Williams has agreed to use its reasonable best
efforts to obtain an opinion ("Tax Opinion") of Skadden, Arps, Slate, Meagher &
Flom, LLP (which includes its affiliated law practice entities) or another
nationally recognized United States federal income tax counsel or "Big Five"
accounting firm that, based on the facts and customary representations and
assumptions, the Offer and the Forward Merger will be treated as a
"reorganization" within the meaning of Section 368(a) of the Code. Williams
expects to be able to obtain the Tax Opinion if (i) the Offer is consummated
and, as expected, the proposed Forward Merger occurs in the ordinary course
after consummation of the Offer, (ii) Williams and Barrett Resources are able to
deliver customary representations to such counsel or "Big Five" accounting firm,
(iii) there is no adverse change in United States federal income tax law and
(iv) at the Effective Time of the Forward Merger, the aggregate fair market
value of the Williams Common Stock delivered as consideration pursuant to the
Forward Merger is greater than 40% of the sum of (a) the aggregate fair market
value of such Williams Common Stock and (b) the aggregate amount of cash paid
pursuant to the Offer and the Forward Merger.

      The Tax Opinion is not a condition to consummating the Offer or the
Merger. If Williams obtains the Tax Opinion, then the Merger will be effected as
a Forward Merger (and the United States federal income tax consequences will be
as summarized above). An opinion of counsel or "Big Five" accounting firm is not
binding on the IRS or any court. If Williams is not able to obtain the Tax
Opinion, then Williams may, at its reasonable discretion, change the Merger in
form from a Forward Merger to a merger of Purchaser (or another direct or
indirect wholly-owned subsidiary of Williams) with and into Barrett Resources
("Reverse Merger"), which, as summarized below, will be a fully taxable
transaction for all holders of Shares (but not for Williams, Purchaser or
Barrett Resources). It is anticipated that Williams will exercise its discretion
to change the Merger to a Reverse Merger from a Forward Merger if Williams is
unable to obtain the Tax Opinion.

      In the event of the Reverse Merger, the tax consequences to holders of
Shares would differ materially from those summarized above. In particular,
although a holder of Shares that has all of its Shares accepted for tender in
the Offer will recognize gain or loss for United States federal income tax
purposes (as summarized above) regardless of whether the Merger is effected as a
Forward Merger or a Reverse Merger or is otherwise treated as part of a
"reorganization", all other holders of Shares would be taxed as follows: Each
holder of Shares that has any of its tendered Shares accepted for tender in the
Offer will recognize capital gain or loss in an amount equal to the difference
between the amount of cash received and the holder's tax basis in such Shares.
The capital gain or loss will be long-term capital gain or loss if the holder
has held such Shares for more than one year at the time such Shares are
purchased in the Offer. Each holder of Shares that exchanges any of its Shares
for Williams Common Stock pursuant to the Reverse Merger will recognize capital
gain or loss in an amount equal to the difference between the fair market value
of the Williams Common Stock received pursuant to the Reverse Merger (including
any cash received in lieu of a fractional share of Williams Common Stock) and
the holder's tax basis in such Shares. The capital gain or loss will be
long-term capital gain or loss if the holder has held the Shares surrendered in
the Reverse Merger for more than one year at the Effective Time of the Reverse
Merger.

      The determination by counsel or a "Big Five" accounting firm as to whether
the Offer and the proposed Forward Merger will be treated as a "reorganization"
within the meaning of Section 368(a) of the Code will depend upon the facts and
law existing at the Effective Time of the proposed Forward Merger. It is
possible that Williams will not be able to obtain the Tax Opinion. THUS, NO
ASSURANCE CAN BE GIVEN THAT THE FORM OF THE MERGER WILL BE A FORWARD MERGER AS
OPPOSED TO A FULLY TAXABLE REVERSE MERGER.

                                        13
   23

6. PRICE RANGE OF THE SHARES; DIVIDENDS.

      According to Barrett Resources' Annual Report on Form 10-K for the fiscal
year ended December 31, 2000 (the "Barrett Resources 10-K"), the Shares are
principally traded on the NYSE under the symbol "BRR." The following table sets
forth, for the periods indicated, the reported high and low sale prices for the
Shares on the NYSE as reported in the Barrett Resources 10-K with respect to
periods occurring in fiscal 1999 and 2000, and as reported by published
financial sources with respect to the first fiscal quarter in 2001 and the
current fiscal quarter.

QUARTER ENDED                                                 HIGH      LOW
- -------------                                                ------    ------
                                                                 
March 31, 1999.............................................  $28.00    $15.44
June 30, 1999..............................................  $39.81    $24.31
September 30, 1999.........................................  $41.25    $32.25
December 31, 1999..........................................  $37.31    $23.06
March 31, 2000.............................................  $34.31    $19.19
June 30, 2000..............................................  $41.63    $27.31
September 30, 2000.........................................  $39.19    $26.69
December 31, 2000..........................................  $59.81    $35.63
March 31, 2001.............................................  $63.00    $42.75
June 30, 2001 (through May 11, 2001).......................  $72.00    $59.41

      According to the Barrett Resources 10-K, Barrett Resources has not paid
any cash dividends since its inception. Under the terms of the Merger Agreement,
Barrett Resources is not permitted to declare or pay dividends with respect to
the Shares, without the prior written consent of Williams and Purchaser.

      On May 4, 2001, the last full day of trading of Shares prior to the
announcement of the execution of the Merger Agreement, the reported closing
price per Share on the NYSE was $67.30 and on March 6, 2001, the last full
trading day before Shell Oil Company disclosed its unsolicited offer for Barrett
Resources, the reported closing price per Share on the NYSE was $45.62. On May
11, 2001, the last full day of trading of Shares prior to the commencement of
the Offer, the reported closing price per Share on the NYSE was $71.08.

      STOCKHOLDERS ARE URGED TO OBTAIN CURRENT MARKET QUOTATIONS FOR THE SHARES.

7. POSSIBLE EFFECTS OF THE OFFER ON THE MARKET FOR THE SHARES; NYSE LISTING;
   EXCHANGE ACT REGISTRATION; MARGIN REGULATIONS.

      POSSIBLE EFFECTS OF THE OFFER ON THE MARKET FOR THE SHARES.  The purchase
of Shares pursuant to the Offer will reduce the number of Shares that might
otherwise trade publicly and could adversely affect the liquidity and market
value of the remaining Shares held by the public. The purchase of Shares
pursuant to the Offer can also be expected to reduce the number of holders of
Shares. We cannot predict whether the reduction in the number of Shares that
might otherwise trade publicly would have an adverse or beneficial effect on the
market price for, or marketability of, the Shares or whether it would cause
future market prices to be more than or less than the Offer Price.

      As discussed earlier, if the Offer is completed and the Barrett Resources'
stockholders approve and adopt the Merger Agreement and the Merger, Williams
will issue 1.767 shares of Williams Common Stock in the Merger upon the exchange
of each then remaining Share of Barrett Resources (other than Shares held by
Barrett Resources, Williams, Purchaser or any other subsidiary of Williams),
including Shares not purchased as a result of proration. The exchange ratio of
1.767 shares of Williams Common Stock per Share is a fixed ratio that will not
be adjusted as a result of any increase or decrease in the price of either the
shares of Williams Common Stock or the Shares. AS A RESULT OF THE FIXED EXCHANGE
RATIO, FLUCTUATIONS IN THE MARKET VALUE OF THE WILLIAMS COMMON STOCK WILL LIKELY
AFFECT THE MARKET VALUE OF THE BARRETT RESOURCES SHARES OUTSTANDING AFTER
COMPLETION OF THE OFFER.

                                        14
   24

      As described above, various factors may affect the market price of shares
of Williams Common Stock, including changes in the business, operations, or
prospects of Barrett Resources or Williams and general market and economic
conditions. To a large extent, these factors are beyond our control or that of
Williams or Barrett Resources. See "Introduction".

      NYSE LISTING.  We do not anticipate that the Shares would be subject to
delisting by the NYSE as a result of completion of the Offer. According to the
NYSE's published guidelines, the NYSE would consider delisting the Shares if,
among other things, (a) the number of record holders of 100 or more Shares
should fall below 1,200; (b) the number of publicly held Shares (exclusive of
holdings of Purchaser and Williams and any other subsidiaries or affiliates of
Barrett Resources and of officers or directors of Barrett Resources or their
immediate families or other concentrated holdings of 10% or more ("Excluded
Holdings")) should fall below 600,000; or (c) the aggregate market value of such
publicly held Shares (exclusive of Excluded Holdings) should fall below
$5,000,000. If, as a result of the purchase of Shares pursuant to the Offer or
otherwise, the Shares no longer meet the requirements of the NYSE for continued
listing and the listing of the Shares is discontinued, the market for the Shares
could be adversely affected.

      If the NYSE were to delist the Shares, it is possible that the Shares
would trade on one or more securities exchanges or in the over-the-counter
market and that price or other quotations would be reported by such exchanges or
through the Nasdaq National Market ("NASDAQ") or other sources. The extent of
the public market for the Shares and the availability of such quotations would
depend upon such factors as (i) the number of stockholders and/or the aggregate
market value of the publicly traded Shares remaining at such time, (ii) the
interest in maintaining a market in the Shares on the part of securities firms,
(iii) the possible termination of registration under the Exchange Act, as
described below, and (iv) other factors. We cannot predict whether the reduction
in the number of Shares that might otherwise trade publicly would have an
adverse or beneficial effect on the market price for, or marketability, of the
Shares or whether it would cause future market prices to be greater or less than
the Offer Price.

      EXCHANGE ACT REGISTRATION.  The Shares are currently registered under the
Exchange Act. Purchaser does not anticipate that such registration will be
subject to termination as a result of completion of the Offer. Registration of
the Shares may be terminated upon application by Barrett Resources to the SEC if
the Shares are not listed on a "national securities exchange" and there are
fewer than 300 record holders of Shares. Termination of registration of the
Shares under the Exchange Act would substantially reduce the information that
Barrett Resources would be required to furnish to its stockholders and the SEC
and would make certain provisions of the Exchange Act, such as the short-swing
profit recovery provisions of Section 16(b) and the requirements of furnishing a
proxy statement in connection with stockholders' meetings pursuant to Section
14(a) or 14(c) and the related requirement of an annual report to stockholders,
no longer applicable to Barrett Resources. If the Shares were no longer
registered under the Exchange Act, the requirements of Rule 13e-3 under the
Exchange Act with respect to "going private" transactions would no longer be
applicable to Barrett Resources. In addition, the ability of "affiliates" of
Barrett Resources and persons holding "restricted securities" of Barrett
Resources to dispose of such securities pursuant to Rule 144 promulgated under
the Securities Act may be impaired or, with respect to certain persons,
eliminated. If registration of the Shares under the Exchange Act were
terminated, the Shares would no longer be "margin securities" or eligible for
stock exchange listing or NASDAQ reporting.

      If registration of the Shares is not terminated prior to the Merger, then
the registration of the Shares under the Exchange Act and the listing of the
Shares on the NYSE will be terminated following the completion of the Merger.

      MARGIN REGULATIONS.  The Shares are currently "margin securities" under
the regulations of the Board of Governors of the Federal Reserve System, which
have the effect, among other things, of allowing brokers to extend credit on the
collateral of the Shares for the purpose of buying, carrying or trading in
securities ("Purpose Loans"). Depending upon factors such as the number of
record holders of the Shares and the number and market value of publicly held
Shares, following the purchase of Shares pursuant to

                                        15
   25

the Offer, the Shares may no longer constitute "margin securities" for purposes
of the Federal Reserve Board's margin regulations and, therefore, could no
longer be used as collateral for Purpose Loans made by brokers. In addition, if
registration of the Shares under the Exchange Act were terminated, the Shares
would no longer constitute "margin securities". Purchaser does not anticipate
that the Shares would not constitute "margin securities" as a result of the
completion of the Offer.

8. CERTAIN INFORMATION CONCERNING BARRETT RESOURCES.

      Barrett Resources' principal executive offices are located at 1515
Arapahoe Street, Tower 3, Suite 1000, Denver, CO 80202. Its telephone number at
such offices is (303) 572-3900. The following description of Barrett Resources
and its business and the selected financial information set forth below have
been taken from the Barrett Resources 10-K and are qualified in their respective
entireties by reference to the Barrett Resources 10-K. None of Purchaser,
Williams, the Dealer Manager or the Information Agent assumes any responsibility
for the accuracy or completeness of the information concerning Barrett Resources
contained in such documents and records or for any failure by Barrett Resources
to disclose events that may have occurred or may affect the significance or
accuracy of any such information.

      Barrett Resources is an independent gas and oil exploration and production
company. Barrett Resources' core areas of activity are in the Rocky Mountain
Region of Colorado, Wyoming and Utah and the Mid-Continent Region of Kansas and
Oklahoma. At December 31, 2000, Barrett Resources' estimated proved reserves
were 1,372 billion cubic feet of natural gas equivalent ("Bcfe") (96% natural
gas and 4% crude oil) with an implied reserve life of 11.6 years based on total
production in 2000 of 117.6 Bcfe. On April 24, 2001, Barrett Resources issued a
press release announcing that, after a review by independent reservoir
engineers, the estimate of Barrett Resources' proved gas and oil reserves had
been raised from 1,372 Bcfe to approximately 2,100 Bcfe. See "-- Certain
Financial Projections And Other Information (Unaudited) -- Gas and Oil Reserve
Information", below. Barrett Resources' net daily production averaged 321
million cubic feet of gas equivalent ("Mcfe") per day for the year ended
December 31, 2000. As of December 31, 2000, Barrett Resources owned an interest
in 4,284 wells, of which 3,441 were producing. Of these producing wells, 2,680
were operated by Barrett Resources. These operated wells contributed
approximately 91% of Barrett Resources' natural gas and oil production for the
year ended December 31, 2000. Barrett Resources also owns and operates a natural
gas gathering system, a 27-mile pipeline and a natural gas processing plant in
the Piceance Basin. Barrett Resources markets all of its own natural gas and oil
production from wells that it operates. In addition, Barrett Resources engages
in natural gas trading activities, which involve purchasing natural gas from
third parties and selling natural gas to other parties at prices and volumes
that management anticipates will result in profits to Barrett Resources.

                                        16
   26

                         SELECTED FINANCIAL INFORMATION

      Set forth below is certain selected consolidated financial information
relating to Barrett Resources and its subsidiaries with respect to the twelve
months ended December 31, 2000, 1999, and 1998 that has been excerpted or
derived from the financial statements contained in the Barrett Resources 10-K.
Also set forth below is certain unaudited consolidated summary information
relating to Barrett Resources and its subsidiaries with respect to the three
months ended March 31, 2001 that has been excerpted or derived from the
financial statements contained in the soliciting material on Schedule 14A filed
by Barrett Resources on May 1, 2001 pursuant to Rule 14a-12 under the Exchange
Act and certain unaudited consolidated summary information with respect to the
three months ended March 31, 2000 that has been excerpted or derived from the
financial statements contained in the Form 10-Q filed by Barrett Resources on
May 15, 2000. More comprehensive information is included in the Barrett
Resources 10-K and other documents filed by Barrett Resources with the SEC. The
financial information that follows is qualified in its entirety by reference to
such reports and other documents, including the financial statements and related
notes contained therein. Such reports and other documents may be examined and
copies may be obtained from the SEC in the manner set forth below.

                         BARRETT RESOURCES CORPORATION

                         CONSOLIDATED INCOME STATEMENT

                                     THREE MONTHS ENDED
                                         MARCH 31,
                                   ----------------------         YEAR ENDED DECEMBER 31,
                                        (UNAUDITED)          ----------------------------------
                                      2001         2000         2000         1999        1998
                                   ----------    --------    ----------    --------    --------
                                              (IN THOUSANDS, EXCEPT PER SHARE DATA)
                                                                        
Operating Revenues...............  $  164,983    $ 69,111    $  376,432    $215,000    $211,768
Net income (loss)................  $   57,012    $  7,826    $   27,674    $ 20,828    $(93,743)
Net income (loss) per share......  $     1.67    $   0.24    $     0.83    $   0.64    $  (2.95)
Total assets at the end of each
  period.........................  $1,162,770    $967,358    $1,253,833    $884,301    $838,879
Long-term debt at the end of each
  period.........................  $  295,005    $384,595    $  406,269    $355,250    $334,067

                                        17
   27

                           CONSOLIDATED BALANCE SHEET

                                                         MARCH 31,     DECEMBER 31,    DECEMBER 31,
                                                           2001            2000            1999
                                                        -----------    ------------    ------------
                                                        (UNAUDITED)
                                                             (IN THOUSANDS, EXCEPT SHARE DATA)
                                                                              
                                              ASSETS
Current assets:
  Cash and cash equivalents...........................  $   22,830      $   25,454       $ 20,634
  Receivables, net....................................     177,519         297,766         99,906
  Gas inventory held for sale, at market..............         855          27,418         19,907
  Deferred income tax assets..........................      26,372              --             --
  Other current assets................................      18,436          29,042         14,075
                                                        ----------      ----------       --------
          Total current assets........................     246,012         379,680        154,522
Other assets:
Net property and equipment (full cost method).........     907,494         869,606        726,489
Other assets, net.....................................       9,264           4,547          3,290
                                                        ----------      ----------       --------
          Total Assets................................  $1,162,770      $1,253,833       $884,301
                                                        ==========      ==========       ========
                               LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable....................................  $  147,352      $  234,739       $ 94,293
  Amounts payable to oil and gas property owners......      13,144          18,672          5,879
  Production taxes payable............................      44,039          39,229         22,981
  Accrued and other liabilities.......................      20,571          20,917         16,610
  Unrealized mark to market transactions..............      81,793          47,745             --
                                                        ----------      ----------       --------
          Total current liabilities...................     306,899         361,302        139,763
Long term debt........................................     295,005         406,269        355,250
Deferred income taxes.................................      52,560          39,003         25,640
Unrealized mark to market transactions................      87,779          31,446             --
Other long-term liabilities...........................      20,000              --             --
                                                        ----------      ----------       --------
          Total liabilities...........................     762,243         838,020        520,653
Commitments and contingencies
Stockholders' equity:
  Common stock, $.01 par value: 45,000,000 shares
     authorized and 33,461,004 shares issued and
     outstanding at March 15, 2001 (33,394,063 at
     December 31, 2000)...............................         335             334            326
  Additional paid-in capital..........................     298,534         296,043        271,560
  Retained earnings...................................     176,446         119,436         91,762
  Accumulated other comprehensive loss................     (74,525)             --             --
  Treasury Stock, at cost.............................        (263)             --             --
                                                        ----------      ----------       --------
          Total stockholders' equity..................     400,527         415,813        363,648
                                                        ----------      ----------       --------
          Total liabilities and stockholders'
            equity....................................  $1,162,770      $1,253,833       $884,301
                                                        ==========      ==========       ========

      Barrett Resources files annual, quarterly and special reports, proxy
statements and other information with the SEC. You may read and copy any
reports, statements or other information filed at the SEC's public reference
room at 450 Fifth Street, N.W., Washington, D.C. 20549, or at the SEC's public
reference rooms in New York, New York and Chicago, Illinois. Please call the SEC
at 1-800-SEC-0330 for further information on the public reference rooms. Barrett
Resources' SEC filings are also available to

                                        18
   28

the public from commercial document retrieval services and at the Internet world
wide web site maintained by the SEC at http://www.sec.gov.

      Although we have no knowledge that any such information is untrue, we take
no responsibility for the accuracy or completeness of information contained in
this Offer to Purchase with respect to Barrett Resources or any of its
subsidiaries or affiliates or for any failure by Barrett Resources to disclose
events which may occur or may have occurred or may affect the significance or
accuracy of any such information.

        CERTAIN FINANCIAL PROJECTIONS AND OTHER INFORMATION (UNAUDITED)

      In the course of Williams' due diligence review of Barrett Resources,
Barrett Resources provided to Williams a Five-Year Strategic Projection as part
of Barrett Resources' March 2001 plan detailing Barrett Resources' forecasts for
certain operational and financial items (the "Projections"). The Projections
were based on numerous assumptions and management estimates. The Projections
also assumed a reserve development scenario contained in an internal reserve
report which included Barrett Resources' estimates of proved and unproved gas
and oil reserves. The actual results may vary materially from the Projections.
Certain information derived from the Projections has been set forth below for
the limited purpose of giving stockholders access to certain projections and
other information provided by Barrett Resources' management to Williams in
connection with its due diligence review of Barrett Resources. In addition, in
connection with Williams' due diligence review of Barrett Resources, Barrett
Resources also provided Williams access in its data room to a set of projections
prepared by Barrett Resources in February 2001, which projections were less
optimistic than the projections included in the Projections described below.

THE PROJECTED FINANCIAL, GAS AND OIL RESERVE AND OTHER INFORMATION SET FORTH
BELOW NECESSARILY REFLECTS NUMEROUS ASSUMPTIONS WITH RESPECT TO GENERAL BUSINESS
AND ECONOMIC CONDITIONS AND OTHER MATTERS, INCLUDING ESTIMATES OF FUTURE PRICES
AND GAS AND OIL RESERVES, MANY OF WHICH ARE INHERENTLY UNCERTAIN OR BEYOND
BARRETT RESOURCES', WILLIAMS' OR PURCHASER'S CONTROL, AND DOES NOT TAKE INTO
ACCOUNT ANY CHANGES IN BARRETT RESOURCES' OPERATIONS OR CAPITAL STRUCTURE WHICH
MAY RESULT FROM THE OFFER AND THE MERGER. IT IS NOT POSSIBLE TO PREDICT WHETHER
THE ASSUMPTIONS MADE IN PREPARING THE PROJECTIONS WILL BE VALID, AND ACTUAL
PRICES, GAS AND OIL RESERVE AMOUNTS AND RESULTS MAY PROVE TO BE MATERIALLY
HIGHER OR LOWER THAN THOSE CONTAINED IN THE PROJECTIONS. THE INCLUSION OF
INFORMATION FROM THE PROJECTIONS SHOULD NOT BE REGARDED AS AN INDICATION THAT
WILLIAMS OR BARRETT RESOURCES CONSIDERED IT A RELIABLE PREDICTOR OF FUTURE
EVENTS, AND THIS INFORMATION SHOULD NOT BE RELIED ON AS SUCH BY BARRETT
RESOURCES' STOCKHOLDERS. NONE OF BARRETT RESOURCES, PURCHASER, WILLIAMS, THE
DEALER MANAGER, THE INFORMATION AGENT OR ANY OF THEIR RESPECTIVE REPRESENTATIVES
ASSUMES ANY RESPONSIBILITY FOR THE VALIDITY, REASONABLENESS, ACCURACY OR
COMPLETENESS OF THE PROJECTIONS, AND BARRETT RESOURCES HAS MADE NO
REPRESENTATIONS OR WARRANTIES TO WILLIAMS OR PURCHASER REGARDING SUCH
INFORMATION.

                                        19
   29

  Financial Projections.

                         BARRETT RESOURCES CORPORATION

                     SELECTED INCOME STATEMENT INFORMATION

                                    2001        2002         2003          2004          2005
                                  --------    --------    ----------    ----------    ----------
                                                      (THOUSANDS OF DOLLARS)
                                                                       
Revenue.........................  $420,890    $657,847    $1,012,964    $1,285,639    $1,541,345
Production costs................   231,846     317,075       446,187       569,970       686,634
Operating profit................   189,044     340,773       566,776       715,669       854,711
Net income before taxes.........   208,361     315,479       551,683       708,794       855,211
Net income......................   129,184     195,597       342,044       439,452       530,231

                       SELECTED BALANCE SHEET INFORMATION

                                  2001          2002          2003          2004          2005
                               ----------    ----------    ----------    ----------    ----------
                                                     (THOUSANDS OF DOLLARS)
                                                                        
ASSETS
Current Assets...............  $  388,157    $  393,023    $  401,289    $  565,288    $1,087,212
Property and equipment,
  net........................   1,037,083     1,303,675     1,534,218     1,627,375     1,639,533
Other assets.................       4,547         4,547         4,547         4,547         4,547
                               ----------    ----------    ----------    ----------    ----------
     Total assets............  $1,429,787    $1,701,245    $1,940,054    $2,197,210    $2,731,293
LIABILITIES AND STOCKHOLDERS
  EQUITY
Current Liabilities..........  $  331,568    $  326,494    $  326,494    $  326,494    $  326,495
Long-term debt...............     405,000       405,000       210,000            --            --
Deferred income taxes
  payable....................     116,777       217,711       309,477       337,181       341,032
Other long-term
  liabilities................      31,446        11,446        11,446        11,446        11,446
Total stockholders' equity...     544,997       740,593     1,082,637     1,522,089     2,052,320
                               ----------    ----------    ----------    ----------    ----------
     Total liabilities and
       stockholder's
       equity................  $1,429,787    $1,701,245    $1,940,054    $2,197,210    $2,731,293

                            PROJECTED SELECTED ITEMS

                                                       2001    2002    2003     2004     2005
                                                       ----    ----    -----    -----    -----
                                                                          
Production (Bcfe)....................................  129      188      257      326      393
Reserve additions (Bcfe).............................  381     1138      703      713      787
Capital investment ($ millions)......................  273      413      417      327      285
Production taxes (% of revenue)......................  9.0%     9.6%     9.6%     9.9%    10.0%
Total revenue ($ millions)...........................  421      658    1,013    1,286    1,541
EBITDA ($ millions)..................................  294      488      753      950    1,128

Financial Assumptions.

      In preparing the Projections, Barrett Resources made numerous assumptions,
including, without limitation, those assumptions set forth in the following
table. Such assumptions were based upon Barrett Resources' management's
forecasts and estimates of future conditions. In addition to estimating items
such as gas prices, costs, tax rates and depletion, depreciation and
amortization, Barrett Resources' management also relied on production estimates
based on development drilling at higher rates than that currently taking place,
as well as other projects that Williams may or may not choose to pursue. It is
not possible to

                                        20
   30

predict whether these assumptions made in preparing the Projections will be
valid, and actual items assumed may prove to be materially different than those
contained in these assumptions.

                         CERTAIN FINANCIAL ASSUMPTIONS

                                                 2001      2002      2003      2004      2005
                                                ------    ------    ------    ------    ------
                                                                         
NYMEX gas price per Mcf.......................  $ 4.50    $ 4.50    $ 4.50    $ 4.50    $ 4.50
Realized gas sales price per Mcf..............  $ 3.22    $ 3.46    $ 3.93    $ 3.94    $ 3.92
Realized oil sales price per bbl..............  $24.00    $24.00    $24.00    $24.00    $24.00
Average lease operating expenses per Mcfe
  (including transportation & gathering)......  $ 0.48    $ 0.47    $ 0.45    $ 0.47    $ 0.49
Average production tax rate...................    9.00%     9.60%     9.60%     9.90%    10.00%
Average total production costs per Mcfe.......  $ 0.83    $ 0.84    $ 0.84    $ 0.86    $ 0.89
Depletion, depreciation & amortization rate
  per Mcfe....................................  $ 0.82    $ 0.78    $ 0.72    $ 0.72    $ 0.70

  Gas and Oil Reserve Information.

      As part of the due diligence process, Barrett Resources provided Williams
with certain information related to its "booked/proved" gas and oil reserves, as
well as certain estimates of "unbooked/unproved" reserves. Barrett Resources
indicated in information provided during the due diligence process that it had
booked/proved gas and oil reserves of 1,372 Bcfe and 8,008 Bcfe in
unbooked/unproved reserves. Of the 8,008 Bcfe of unbooked/unproved reserves,
approximately 5,385 Bcfe of the unbooked/unproved reserves were attributable to
the Piceance and Powder River Basins, and approximately 1,629 Bcfe of the
unbooked/unproved reserves were attributable to exploration activities. On April
24, 2001 and subsequent to Williams' receipt of the foregoing reserve estimates,
Barrett Resources issued a press release announcing that, after a review by
independent reservoir engineers, the estimate of Barrett Resources' proved gas
and oil reserves had been raised from 1,372 Bcfe to approximately 2,100 Bcfe; no
further information was provided to Williams by Barrett Resources regarding how
and to what extent the booking of these additional proved reserves would affect
the estimates of unbooked/unproven reserves. According to Barrett Resources, the
estimates of "unbooked/unproved" reserves that Barrett Resources provided to
Williams were attributable to Barrett Resources' belief in the potential for
significant growth in its natural gas reserves and production due to, among
other things, its large acreage position in the Piceance Basin (134,000 net
acres) and the Powder River Basin (476,000 net acres), geological and reservoir
engineering data, increases in production and its exploration activities.

      Proved reserves are the estimated quantities of crude oil, natural gas and
natural gas liquids which geological and engineering data demonstrate with
reasonable certainty to be recoverable in future years from known reservoirs
under existing economic and operating conditions. Proved reserves are limited to
those quantities of oil and gas which can be expected, with little doubt, to be
recoverable commercially at current prices and costs, under existing regulatory
practices and with existing conventional equipment and operating methods.
Estimates of unbooked/unproved reserves are based upon analysis of geological
and engineering data which does not demonstrate such reserves to be proved under
existing economic and operating conditions, but indicates where such analysis
suggests some likelihood of their existence and future recovery. ESTIMATES OF
UNPROVED RESERVES ARE HIGHLY SPECULATIVE, SHOULD NOT BE REGARDED AS AN
INDICATION THAT WILLIAMS OR BARRETT RESOURCES CONSIDERS THEM A RELIABLE
PREDICTOR OF FUTURE PROVED RESERVES AND THIS INFORMATION SHOULD NOT BE RELIED ON
AS SUCH. IN ADDITION, IT MAY NOT BE ECONOMICAL TO RECOVER UNBOOKED/UNPROVED
RESERVES IF THERE IS A DECLINE IN THE MARKET PRICE IN OIL AND GAS. THE ABILITY
TO PRODUCE UNBOOKED/UNPROVED RESERVES IS ALSO HIGHLY DEPENDENT ON GOVERNMENTAL
REGULATIONS RELATING TO DRILLING OF OIL AND GAS WELLS.

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      CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS.  Certain
matters discussed herein, including without limitation, the Projections and the
reserve information, are forward-looking statements that involve risks and
uncertainties. Such information has been included in this Offer to Purchase for
the limited purpose of giving Barrett Resources' stockholders access to
projections and other information prepared by Barrett Resources' management that
were made available to Williams. The Projections were based on assumptions
concerning Barrett Resources' operations and business prospects in 2001 through
2005, including the assumption that Barrett Resources would continue to operate
under the same ownership structure as existed at the time the Projections were
prepared. The Projections were also based on other revenue, expense and
operating assumptions. Information of this type is based on estimates and
assumptions that are inherently subject to significant economic and competitive
uncertainties and contingencies, all of which are also difficult to predict and
many of which are beyond Barrett Resources' and Williams' control. Such
uncertainties and contingencies include, but are not limited to, the following
factors: changes in the economic conditions in which Barrett Resources operates,
including fluctuations in demand, seasonally and otherwise; greater than
anticipated competition or price pressures; changes in market prices for gas and
oil; new or alternative product offerings; better or worse than expected
customer consumption resulting in the need to expand operations and make capital
investments; the availability of resources to recover gas and oil reserves and
the impact of investments required to enter new markets or remain competitive in
established markets. Accordingly, there can be no assurance that the projected
results would be realized or that actual results would not be significantly
higher or lower than those set forth above. In addition, the Projections and
other forward-looking information were not prepared with a view to public
disclosure or compliance with the published guidelines of the SEC or the
guidelines established by the American Institute of Certified Public Accountants
regarding projections and forecasts, and are included in this Offer to Purchase
only because such information was made available to Williams by Barrett
Resources. Neither Williams', Purchaser's nor Barrett Resources' independent
accountants or independent reservoir engineers have examined, compiled or
applied any agreed upon procedures to this information, and, accordingly, do not
express an opinion or any form of assurance with respect thereto and assume no
responsibility for this information. Neither Williams, Purchaser nor Barrett
Resources intends to provide any updated information with respect to the
Projections, reserve information or any forward-looking statements.

9. CERTAIN INFORMATION CONCERNING WILLIAMS AND PURCHASER

      Williams is a Delaware corporation with its principal executive offices
located at One Williams Center, Tulsa, OK 74172. Its telephone number at such
offices is (918) 573-2000. Williams, together with its subsidiaries, is a
leading company in the energy sector. Williams and its subsidiaries are
principally dedicated to energy-related activities, including transportation and
storage of natural gas and related activities; exploration and production of oil
and gas; natural gas gathering, processing and treating activities; natural gas
liquids transportation; transportation of petroleum products and related
terminal services; light hydrocarbon/olefin transportation; ethylene production;
production and marketing of ethanol and bio-products; refining of petroleum
products; retail marketing; and energy commodity marketing and trading. The
name, business address, citizenship, present principal occupation and employment
history for the past five years of each of the directors and executive officers
of Williams are set forth in Schedule I.

      Purchaser is a Delaware corporation with its principal executive offices
located at One Williams Center, Tulsa, OK 74172. Its telephone number at such
offices is (918) 573-2000. Purchaser is a wholly-owned subsidiary of Williams.
Purchaser has not carried on any activities other than in connection with the
Offer and the Merger. The name, business address, citizenship, present principal
occupation and employment history for the past five years of each of the
directors and executive officers of Purchaser are set forth in Schedule I.

      On April 23, 2001, Williams completed the spinoff (the "Spinoff") of
Williams Communications Group, Inc. ("WCG"), Williams' former telecommunications
business, through a tax-free distribution of 398.5 million WCG shares to
Williams' stockholders. This distribution amounted to approximately 95 percent
of the WCG shares held by Williams. After the close of market on April 23, 2001,
Williams

                                        22
   32

stockholders were issued 0.822399 of a share of WCG common stock for each share
of Williams Common Stock held, with cash in lieu of fractional shares. On or
before May 15, 2001, Williams expects to file with the SEC its Quarterly Report
on Form 10-Q for the quarter ended March 31, 2001, which will contain financial
disclosure and other information regarding the Spinoff.

      Williams is subject to the information and reporting requirements of the
Exchange Act and is required to file periodic reports, proxy statements and
other information with the SEC relating to its business, financial condition and
other matters. Certain information, as of particular dates, concerning Williams'
business, principal physical properties, capital structure, material pending
legal proceedings, operating results, financial condition, directors and
officers (including their remuneration and stock options granted to them), the
principal holders of Williams' securities, any material interests of such
persons in transactions with Williams and certain other matters is required to
be disclosed in proxy statements and annual reports distributed to Williams'
stockholders and filed with the SEC. You may inspect or copy these reports,
proxy statements and other information at the SEC's public reference facilities
and they should also be available for inspection in the same manner as set forth
above with respect to Barrett Resources in Section 8 of this document.

      Except as set forth elsewhere in this Offer to Purchase or Schedule I
hereto: (a) neither Williams, Purchaser nor, to our knowledge, any of the
persons listed in Schedule I hereto or any associate or majority-owned
subsidiary of ours or of any of the persons so listed, beneficially owns or has
a right to acquire any Shares or any other equity securities of Barrett
Resources; (b) neither Williams, Purchaser, nor, to our knowledge, any of the
persons or entities referred to in clause (a) above or any of their executive
officers, directors or subsidiaries has effected any transaction in the Shares
or any other equity securities of Barrett Resources during the past 60 days; (c)
neither Williams, Purchaser nor, to our knowledge, any of the persons listed in
Schedule I hereto, has any contract, arrangement, understanding or relationship
with any other person with respect to any securities of Barrett Resources
(including, but not limited to, any contract, arrangement, understanding or
relationship concerning the transfer or the voting of any such securities, joint
ventures, loan or option arrangements, puts or calls, guaranties of loans,
guaranties against loss or the giving or withholding of proxies, consents or
authorizations); (d) since May 7, 1999, there have been no transactions which
would require reporting under the rules and regulations of the SEC between
Williams or any of its subsidiaries or, to our knowledge, any of the persons
listed in Schedule I hereto, on the one hand, and Barrett Resources or any of
its executive officers, directors or affiliates, on the other hand; and (e)
since May 7, 1999, there have been no contacts, negotiations or transactions
between Williams or any of its subsidiaries or, to our knowledge, any of the
persons listed in Schedule I hereto, on the one hand, and Barrett Resources or
any of its subsidiaries or affiliates, on the other hand, concerning a merger,
consolidation or acquisition, a tender offer or other acquisition of securities,
an election of directors or a sale or other transfer of a material amount of
assets.

10. BACKGROUND OF THE OFFER.

      As a part of ongoing business development activities, for several months
prior to mid-March 2001, a strategic team within Williams evaluated several
natural gas exploration and production companies as possible acquisition
candidates to complement Williams' other business activities. Barrett Resources
was one of the potential acquisition candidates identified in that process.

      On March 7, 2001, Shell Oil Company ("Shell") issued a press release
announcing an unsolicited proposal to acquire Barrett Resources for $55 per
Share in cash. On March 8, 2001, Barrett Resources issued a press release
announcing that its Board of Directors had reviewed and rejected Shell's
unsolicited proposal and that the Board had authorized management of Barrett
Resources to pursue strategic alternatives, including seeking acquisition
proposals from qualified parties.

      On March 8, 2001, following Shell's announcement of its unsolicited
proposal to acquire Barrett Resources, representatives of Williams contacted a
senior officer of Barrett Resources to indicate Williams' interest in acquiring
Barrett Resources. Thereafter, Barrett Resources' financial advisors, Goldman
Sachs

                                        23
   33

and Petrie Parkman, contacted representatives of Williams in regards to
Williams' participation in Barrett Resources' process.

      On March 9, 2001, Williams entered into a Confidentiality Agreement with
Barrett Resources (the "Confidentiality Agreement") which provided, among other
things, that Williams would keep confidential information it received from
Barrett Resources and would abide by certain "standstill" restrictions until May
11, 2001.

      On March 12, 2001, Shell and a wholly-owned subsidiary of Shell commenced
a cash tender offer for all outstanding Shares at $55 per Share (the "Shell
Offer"). Also on March 12, 2001, Shell filed with the SEC preliminary consent
solicitation materials, pursuant to which Shell stated it would seek to remove
all of Barrett Resources' directors without cause and replace them with three
nominees selected by Shell (the "Shell Consent Solicitation"). A record date of
April 19, 2001 was eventually set by Barrett Resources' Board for the proposed
Shell Consent Solicitation.

      On March 22, 2001, Barrett Resources' Board held a special meeting at
which the Board reviewed the Shell Offer and unanimously concluded that the
Shell Offer was inadequate and not in the best interests of Barrett Resources'
stockholders.

      Commencing in mid-March 2001 and continuing through May 6, 2001, Williams
and its representatives conducted a due diligence review of the business and
financial condition of Barrett Resources. During such period, representatives of
Williams held several discussions with representatives of Barrett Resources
about Williams' interest in Barrett Resources and Barrett Resources' strategic
fit with Williams, including, among others, a few conversations held prior to
the May 2, 2001 bid deadline between Mr. Keith Bailey, Chairman, President and
Chief Executive Officer of Williams, and C. Robert Buford, a director of Barrett
Resources and an acquaintance of Mr. Bailey.

      On or about April 11, 2001, Barrett Resources sent to each party
(including Williams) who signed a confidentiality agreement and visited the data
room (i) a detailed instruction letter for submitting binding proposals to
acquire or merge with Barrett Resources and (ii) two forms of merger agreement
(one for cash proposals and one for stock proposals). The letter indicated that
each party's proposal was due on May 2, 2001 along with any comments and
revisions that each party required to the relevant form(s) of merger agreement.

      On April 26, 2001, Shell announced that it was increasing the price
offered in the Shell Offer from $55 to $60 per Share (the "Revised Shell
Offer"). On April 30, 2001, Barrett Resources announced that it had rejected the
Revised Shell Offer as inadequate and reiterated that Barrett Resources had
invited competing offers as part of a process to review its strategic
alternatives. In response to Shell's request that Barrett Resources consider
Shell's Revised Offer on an equal basis with any other offers, Barrett Resources
invited Shell to participate in the auction process and submit its "best and
final" offer by 12:00 noon, on Wednesday, May 2, 2001, the deadline which
Barrett Resources had established for other interested parties participating in
the "auction process". Barrett Resources also furnished Shell's financial
advisors with the forms of merger agreements it had furnished to other potential
bidders, and advised Shell of the "ground rules" which were also applicable to
other potential bidders.

      On May 1, 2001, the Williams Board of Directors, together with Williams'
financial advisors, held a telephonic meeting for the purpose of considering the
authorization of an acquisition proposal for Barrett Resources. At the beginning
of the telephonic meeting, outside individuals were mistakenly connected by a
conference call vendor. Before this error was discovered, officers of Williams
stated that the Board meeting had been called to consider Williams' potential
proposal to acquire Barrett Resources. As a result of this non-intentional,
inadvertent disclosure, Williams filed a Form 8-K disclosing this event on May
1, 2001.

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   34

      Following approval by the Williams Board of Directors to submit a proposal
to acquire Barrett Resources in accordance with the bid procedures established
by Barrett Resources, Williams sent a proposal letter to Barrett Resources'
financial advisors on May 2, 2001, the form of which is set forth below:

                                                                     May 2, 2001

VIA OVERNIGHT MAIL and FACSIMILE

                                                            
Ray Strong                                                     Jon Hughes
Vice President                                                 Principal
Goldman, Sachs & Co.                                           Petrie Parkman & Co.
85 Broad Street, 19th Floor                                    600 Travis St., Suite 7400
New York, NY 10004                                             Houston, TX 77002
Fax: 212-346-3895                                              Fax: 713-650-8461

      Re: Proposal to Acquire all of the outstanding equity securities of
          Barrett Resources Corporation ("Company")

Dear Messrs. Strong and Hughes:

      In response to your invitation to bid dated April 11, 2001, The Williams
Companies, Inc. ("Williams") hereby submits this bid proposal to acquire 100% of
the outstanding common stock of Barrett Resources Corporation ("Shares") on the
terms set forth in this letter. Except as set forth in that certain
confidentiality agreement dated March 9, 2001 between Williams and Barrett
Resources, neither Williams nor any of its affiliates have any obligation to
Barrett Resources based on this letter or otherwise unless and until each of the
conditions set forth below has been satisfied.

      The material terms and conditions of Williams' proposal are as follows:

             1.  SHARE PRICE.  Williams will pay a price per Share equivalent to
      $71.00 for each outstanding Share.

             2.  STRUCTURE.  The consideration for the Shares will be composed
      of 50% Williams common stock and 50% cash. If desired by Barrett's Board
      of Directors, Williams will increase the common stock component of its
      offer up to 100% of the consideration. The exchange ratio will be fixed at
      the time of the execution of the definitive agreements and be determined
      by the market price of Williams common stock, such market price to be the
      average closing price of Williams stock on the New York Stock Exchange
      ("NYSE") for 10 consecutive days preceding the execution of the definitive
      agreements. Williams believes that an exchange of stock not only provides
      the potential for significant value appreciation but also an attractive
      tax deferral to Barrett stockholders. In the event that Barrett Resources
      desires a combination of cash and Williams common stock, we would propose
      to structure the transaction as a cash tender offer followed by a stock
      for stock merger. The transaction is intended to qualify as a tax-free
      reorganization.

             3.  SOURCE OF FUNDS.  Williams has committed lines of capital
      and/or cash on hand in amount sufficient to pay any cash portion of the
      consideration at the closing.

             4.  COMPANY EMPLOYEES.  Williams admires Barrett and realizes that
      Barrett Resources' success is a direct result of its dedicated, highly
      competent employees. Williams plans on retaining a substantial majority of
      Barrett's employees and maintaining Barrett's offices in Denver. We also
      expect that Williams' northern Rocky Mountain assets, including interests
      in the prolific Jonah Field, will be integrated with Barrett's assets and
      operated out of Denver. Since there is very little

                                        25
   35

      overlap between Barrett's and Williams' core properties, most of Barrett's
      employees can expect to continue in the same capacity in which they
      currently act, with expanded opportunities for future advancement.

             5.  CONDITIONS.  Williams' proposal contained herein is subject to
      the following conditions:

                  a.  DEFINITIVE AGREEMENT.  Williams and Barrett Resources
           shall have entered into a mutually acceptable definitive merger
           agreement containing the terms set forth in this letter and in the
           attached form of merger agreement, as revised.

                  b.  APPROVALS.  The proposal provided herein has been approved
           by the Williams Board of Directors. The following additional
           approvals shall have been obtained: (i) the approval of the board of
           directors of Barrett Resources, (ii) the applicable waiting period
           under the Hart-Scott-Rodino Act shall have expired or been
           terminated, (iii) the Williams common stock to be issued in
           connection with this proposal shall have been registered by the SEC
           and approved for listing on the NYSE, and (iv) the stockholders of
           Barrett Resources shall have tendered at least 50% of the Shares.

             6.  CONFIDENTIALITY.  This Proposal and the price, terms and
      conditions herein are subject to Barrett Resources' agreement that the
      proposal and the price, terms and conditions herein will not be made
      public or otherwise disclosed without the prior consent of Williams.

             7.  NO SOLICITATION; TERMINATION FEE.  Barrett Resources will agree
      to customary non-solicitation of acquisition proposals, including notice
      provisions of third party offers and proposed termination of the merger
      agreement. The merger agreement will provide for a termination fee equal
      to three percent of the value of 100% of the Shares, payable to Williams
      if, among other things, Barrett Resources accepts a "superior" proposal,
      Barrett Resources' board withdraws its recommendation, there is a change
      in the majority of Barrett Resources' board or the minimum tender
      condition is not met and a competing acquisition proposal has been made.

             8.  MANAGEMENT PRESENTATION.  Williams would be pleased to meet as
      soon as practical with the Barrett Board of Directors to describe
      Williams' plans and expectations for the future, the compelling value
      inherent in our common stock, and the reasons we expect our stock to
      continue to perform well relative to the market and industry as a whole.

      We appreciate your consideration of this proposal. In order to help you
understand the upside value of Williams common stock as consideration in an
exchange offer, we have included some backup material to this letter containing
recent analyst comments, earnings estimates, recommendations on Williams, and a
graph showing Williams as a compelling stock value in relation to other
comparable stocks. Williams common stock (ticker: WMB) achieved a total return
of 1345% from January 1, 1990 to April 30, 2001, a compound annual return of
28%. We are including this material solely for informational purposes, and we
assume no responsibility for the accuracy of the factual information contained
therein. As a matter of policy, we do not generally comment on analysts'
projections or estimates and our inclusion of this material should not in any
matter be viewed as agreement or acquiescence on our part with the projections
or opinions set forth in such material.

      Please direct any questions or comments regarding this proposal to Mark
Wilson, Vice President of Corporate Development, at the office at (918)
573-9236, facsimile number (918) 573-2334, at home at . . ., or cell phone at .
 . . We have engaged Skadden, Arps, Slate, Meagher & Flom, LLP as our legal
advisors and Merrill Lynch & Co., Inc. as our financial advisors in connection
with this process.

      We would like to begin negotiation of definitive agreements immediately
and be in a position to sign a definitive merger agreement within one week. This
offer will remain in effect until 5:00 p.m. Central

                                        26
   36

Time on May 9, 2001, whereupon it will automatically expire unless extended by
Williams in its sole discretion.

                                          Sincerely,

                                          THE WILLIAMS COMPANIES, INC.

                                          By: /s/    KEITH E. BAILEY
                                            ------------------------------------
                                                      Keith E. Bailey
                                            Chairman of the Board, President and
                                                             CEO

      The proposal letter was accompanied by proposed changes to the form of
merger agreement relating to a stock proposal furnished by Barrett Resources to
Williams during the "auction process".

      On May 2, 2001, Shell announced that it would maintain its revised offer
price for the Shares at $60 per Share and that is was prepared to negotiate all
terms of its proposal, including price. Shell also announced that it was
submitting a merger agreement to Barrett Resources' financial advisors and that
such merger agreement did not include a "breakup fee."

      On the afternoon of May 4, 2001, representatives of Barrett Resources
advised representatives of Williams that Williams was one of two final bidders
in Barrett Resources' auction process and requested that Williams submit an
amended proposal, if it chose to do so, by 2:00 p.m. (Denver time) on Saturday,
May 5, 2001, and that Williams consider providing more certainty as to value
with respect to the stock portion of its proposal. Commencing on the evening of
May 4, 2001, counsel for Barrett Resources provided to Williams and counsel for
Williams a revised form of merger agreement and related schedules. The revised
merger agreement reflected Barrett Resources' response to the form of merger
agreement which had been submitted by Williams with its May 2(nd) proposal
letter.

      On Saturday, May 5, 2001, representatives of Williams advised Barrett
Resources that Williams was increasing its proposal from $71 to $73 per Share,
while maintaining the structure and other terms set forth in its May 2(nd)
proposal letter, and accepting Barrett Resources' proposed maximum expense
reimbursement amount of $15 million. In addition, counsel for Williams provided
Barrett Resources and its counsel a revised form of merger agreement that
responded to the May 4(th) draft of the merger agreement. During the evening of
May 5, 2001, representatives of Barrett Resources advised Williams that it was
the prevailing bidder in Barrett Resources' auction process. Negotiations with
respect to the draft merger agreement continued through May 6, 2001 and the
early morning hours of May 7.

      On May 6, 2001, representatives of Barrett Resources and its legal and
financial advisors traveled to Williams' headquarters in Tulsa, Oklahoma and
conducted an on-site due diligence review of Williams.

      On the evening of May 6, 2001, the Board of Directors of Williams held a
telephonic meeting at which the Merger Agreement and the transactions
contemplated thereby were approved. At such meeting, Merrill Lynch, financial
advisor to Williams, rendered an oral opinion (which was subsequently confirmed
in writing) that as of the date of the opinion the consideration to be paid in
the Offer and Merger, taken together, was fair from a financial point of view to
Williams. Barrett Resources' Board of Directors held a meeting early in the
morning of May 7, 2001 at which the Merger Agreement and related transactions
were approved. The Merger Agreement was executed on the morning of May 7, 2001
and separate press releases announcing the transaction were issued by each of
Williams and Barrett Resources.

      On May 7, 2001, Shell publicly announced that it was withdrawing its offer
to acquire Barrett Resources.

      On May 14, 2001, Williams and Purchaser commenced the Offer.

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   37

11. PURPOSE OF THE OFFER AND THE MERGER; THE MERGER AGREEMENT; EFFECTS OF
    INABILITY TO CONSUMMATE THE MERGER; STATUTORY REQUIREMENTS; APPRAISAL
    RIGHTS; PLANS FOR BARRETT RESOURCES; CONFIDENTIALITY AGREEMENTS; "GOING
    PRIVATE" TRANSACTIONS.

  Purpose of the Offer

      The purpose of the Offer and the Merger is to acquire control of, and the
entire equity interest in, Barrett Resources. The Offer, as the first step in
the acquisition of Barrett Resources, is intended to facilitate the transaction
by permitting Williams, through Purchaser, to acquire 50% of the Shares on an
expeditious basis. The purpose of the Merger is to acquire all capital stock of
Barrett Resources not purchased pursuant to the Offer or otherwise. Assuming
that all the conditions to the Merger are satisfied, Barrett Resources will
merge with and into Purchaser with Purchaser continuing as the surviving
corporation, unless certain conditions related to the United States federal
income tax treatment of the Offer and the merger of Barrett Resources with and
into Purchaser are not satisfied, in which case Purchaser may, in Williams'
reasonable discretion, merge with and into Barrett Resources with Barrett
Resources as the surviving corporation (whichever shall survive the Merger in
accordance with the foregoing, the "Surviving Corporation"). The Offer is being
made pursuant to the Merger Agreement.

      Under the Delaware General Corporation Law (the "DGCL"), the approval of
Barrett Resources' Board and the affirmative vote of the holders of a majority
of the outstanding Shares are required to approve and adopt the Merger Agreement
and the transactions contemplated thereby, including the Merger. The Board of
Directors of Barrett Resources has unanimously approved the Merger Agreement and
the transactions contemplated thereby and determined that the Merger Agreement
and the terms contemplated thereby, including the Offer and the Merger, are
advisable and are fair to and in the best interests of, Barrett Resources and
its stockholders. The only remaining required corporate action of Barrett
Resources is the Barrett Resources Stockholder Approval. In the Merger
Agreement, Barrett Resources has agreed to convene the Barrett Resources Special
Meeting to seek Barrett Resources Stockholder Approval and the adoption of the
Merger Agreement and the transactions contemplated thereby as promptly as
practicable after the consummation of the Offer and such time as the
registration statement for the conversion of Williams Common Stock for Shares
pursuant to the Merger becomes effective. If Purchaser has acquired (pursuant to
the Offer or otherwise) 50% of the outstanding Shares (which is expected to
occur if the Minimum Condition is met), Purchaser will effectively have
sufficient voting power to approve and adopt the Merger Agreement and the
Merger.

      Purchaser has agreed that all Shares owned by it and any of its affiliates
will be voted in favor of the Merger at the Barrett Resources Special Meeting.

      If Purchaser purchases Shares pursuant to the Offer, the Merger Agreement
provides that Purchaser will be entitled to designate representatives to serve
on the Board of Barrett Resources substantially in proportion to Purchaser's
ownership of Shares following such purchases. See "The Merger Agreement", below.
If Purchaser purchases 16,730,502 Shares in the Offer, Purchaser expects that
such representation would permit Williams to appoint at least one-half of the
members of the Barrett Resources Board.

  The Merger Agreement

      The following summary description of the Merger Agreement is qualified in
its entirety by reference to the Merger Agreement itself, filed as an exhibit to
the Tender Offer Statement on Schedule TO that we filed with the SEC, which you
may examine and copy at the offices of the SEC as set forth in Section 8 (except
that it will not be available at the regional offices of the SEC).

      THE OFFER.  The Merger Agreement provides for the making of the Offer. Our
obligation to accept for payment and pay for Shares tendered pursuant to the
Offer is subject to the satisfaction or waiver of the Minimum Condition and
certain other conditions that are described in Section 14 (collectively, the
"Offer Conditions"). Subject to the provisions of the Merger Agreement, we may
waive any Offer Condition; however, without the prior written consent of Barrett
Resources we can not waive the

                                        28
   38

Minimum Condition. We reserve the right to modify the terms of the Offer, except
that, without the prior written consent of Barrett Resources, we may not (i)
reduce the number of Shares sought in the Offer, (ii) decrease the price per
Share, (iii) impose any conditions to the Offer in addition to the Offer
Conditions or modify the Offer Conditions in a manner adverse to the holders of
Shares (other than to waive any Offer Conditions to the extent permitted by the
Merger Agreement), (iv) except as expressly provided in the Merger Agreement
extend the Offer, (v) change the form of consideration payable in the Offer
(other than by adding consideration) or (vi) make any other change or
modification in any of the terms of the Offer in any manner that is adverse to
the holders of Shares. See Section 14, "Conditions of the Offer".

      On the date of commencement of the Offer, Williams and Purchaser will file
with the SEC a Tender Offer Statement on Schedule TO (the "Schedule TO") with
respect to the Offer and the related Letter of Transmittal, and Williams and
Purchaser will disseminate the Offer Documents (as defined herein) to holders of
Shares. On the date the Offer Documents are filed with the SEC, Barrett
Resources will file with the SEC the Schedule 14D-9 containing the
Recommendations (as defined herein) (subject to the right of the Board of
Directors of Barrett Resources to make a Subsequent Determination (as defined
herein)) and Barrett Resources will disseminate the Schedule 14D-9 to its
stockholders. This Offer to Purchase, the Letter of Transmittal, a Notice of
Guaranteed Delivery and certain related documents are referred to herein as the
"Offer Documents."

      RECOMMENDATION.  The Board of Directors of Barrett Resources duly adopted
resolutions by unanimous vote (i) determining that the Merger Agreement and the
transactions contemplated thereby are advisable and fair to and in the best
interest of Barrett Resources' stockholders, (ii) approving the Merger Agreement
and the transactions contemplated thereby, including the Offer and the Merger,
(iii) waiving the application of Barrett Resources' bylaws (the "Bylaws") with
respect to the Merger Agreement, the Offer and the Merger and (iv) resolving to
recommend acceptance of the Offer and that stockholders of Barrett Resources
tender their Shares in the Offer (collectively, the "Recommendations").

      THE MERGER.  The Merger Agreement provides that the purchase of Shares in
the Offer will be followed by a merger of Barrett Resources with and into
Purchaser in the Forward Merger. However, if Williams is unable (using its
reasonable best efforts) to obtain a written opinion of its legal counsel, or
another nationally recognized United States federal income tax counsel or "Big
Five" accounting firm, that the Offer and the Forward Merger will be treated as
a "reorganization" within the meaning of Section 368(a) of the Code, then in
Williams' reasonable discretion the Merger may be accomplished through the
merger of Purchaser (or another direct or indirect wholly-owned subsidiary of
Williams, as determined by Williams in its reasonable discretion) with and into
Barrett Resources in the Reverse Merger. In each case the Surviving Corporation
of the Merger will become a direct or indirect wholly-owned subsidiary of
Williams.

      If the Forward Merger is effected, then following the Effective Time, the
separate existence of Barrett Resources will cease and Purchaser will continue
as the Surviving Corporation. If the Reverse Merger is effected, then, following
the Effective Time, the separate existence of Purchaser will cease and Barrett
Resources will continue as the Surviving Corporation. The Surviving Corporation
will succeed to and assume all the rights and obligations of Purchaser and
Barrett Resources in accordance with the DGCL.

      The Merger Agreement provides that (i) in the event of the Forward Merger,
each issued and outstanding share of capital stock of Purchaser will remain as
one validly issued, fully paid and nonassessable share of common stock, no par
value, of the Surviving Corporation and (ii) in the event of the Reverse Merger,
each issued and outstanding share of capital stock of Purchaser will be
converted into and become one validly issued, fully paid and non-assessable
share of common stock of the Surviving Corporation.

      As of the Effective Time, each Share (other than Shares held directly or
indirectly by Williams or Barrett Resources or their subsidiaries or by
Purchaser) will be converted into the right to receive 1.767 (the "Exchange
Ratio") duly authorized, validly issued, fully paid and non-assessable shares of
Williams
                                        29
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Common Stock (the "Merger Consideration"). As of the Effective Time, all such
Shares, when converted, shall no longer be outstanding and will automatically be
cancelled and retired, and each holder of a certificate representing any such
Shares will cease to have any rights with respect thereto, except (upon the
surrender of certificates for such Shares or book-entry transfer of such Shares)
(i) the right to receive dividends paid to holders of Williams Common Stock
after the Effective Time, (ii) certificates representing the Williams Common
Stock into which such Shares are converted, and (iii) any cash, without
interest, in lieu of fractional shares of Williams Common Stock to be issued or
paid in consideration therefor.

      No fractional shares of Williams Common Stock will be issued, nor shall
dividends or interest be paid on fractional shares of Williams Common Stock.
Instead of any fractional share of Williams Common Stock that would otherwise be
issuable, cash adjustments will be paid to holders in respect of any fractional
share of Williams Common Stock, and the amount of such cash adjustment will be
equal to the product of (x) such stockholder's fractional share of Williams
Common Stock that would otherwise be issuable to such holder and (y) the closing
price per share of Williams Common Stock on the NYSE on the Closing Date (as
defined in the Merger Agreement) of the Merger.

      REPRESENTATIONS AND WARRANTIES.  Pursuant to the Merger Agreement, Barrett
Resources has made customary representations and warranties to Purchaser and
Williams, including representations relating to its organization and
qualification and subsidiaries; its certificate of incorporation and bylaws;
capital structure; corporate authorizations; absence of conflicts; required
filings and consents; compliance with laws; information supplied; SEC filings;
voting requirements; absence of certain changes or events; absence of
undisclosed liabilities; litigation; employee benefit plans; tax matters;
intellectual property; environmental matters; conditions of assets; and other
matters.

      Pursuant to the Merger Agreement, Purchaser and Williams have made
customary representations and warranties to Barrett Resources, including
representations relating to corporate organization; absence of certain changes
or events; capital structure; SEC filings; corporate authorizations; Williams
Common Stock; information supplied; compliance with laws; absence of conflicts;
financial statements; litigation; and other matters.

      Certain of the representations and warranties contained in the Merger
Agreement are qualified as to "materiality", "Material Adverse Change" or
"Material Adverse Effect". When used in connection with Barrett Resources or
Williams, as the case may be, "Material Adverse Change" or "Material Adverse
Effect" means any change or effect (or any development that, insofar as can
reasonably be foreseen, is likely to result in any change or effect) that is
materially adverse to the business, properties, assets, condition (financial or
otherwise) or results of operations of Barrett Resources and its subsidiaries
taken as a whole, or Williams and its subsidiaries taken as a whole, as the case
may be; provided, however, that (i) any adverse change, effect or development
that is caused by or results from conditions affecting the United States economy
generally or the economy of any nation or region in which Barrett Resources or
Williams, as the case may be, or their respective subsidiaries, conducts
business that is material to the business of Barrett Resources or Williams, as
the case may be, and their respective subsidiaries, taken as a whole, shall not
be taken into account in determining whether there has been (or whether there
could reasonably be foreseen) a "Material Adverse Change" or "Material Adverse
Effect" with respect to Barrett Resources or Williams, as the case may be, (ii)
any adverse change, effect or development that is caused by or results from
conditions generally affecting the industries (including the oil and gas
industry) in which Barrett Resources or Williams, as the case may be, conducts
its business shall not be taken into account in determining whether there has
been (or whether there could be reasonably be foreseen) a "Material Adverse
Change" or "Material Adverse Effect" with respect to Barrett Resources or
Williams, as the case may be, and (iii) any adverse change, effect or
development that is caused by or results from the announcement or pendency of
the Merger Agreement, the Offer, the Merger or the transactions contemplated
thereby will not be taken into account in determining whether there has been (or
whether there could reasonably be foreseen) a "Material Adverse Change" or
"Material Adverse Effect" with respect to Barrett Resources or Williams, as the
case may be.

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   40

      COVENANTS OF WILLIAMS.  Pursuant to the Merger Agreement, Williams has
agreed to comply with various covenants, including:

             Williams' Conduct of Business.  During the period from the date of
      the Merger Agreement until the Effective Time, Williams will, and will
      cause each of its subsidiaries to, in all material respects, except as
      contemplated by the Merger Agreement, carry on its business in the
      ordinary course as currently conducted. During such period, Williams will
      not, and will not permit any of its subsidiaries to, without the prior
      written consent of Barrett Resources (which consent will not be
      unreasonably withheld or delayed):

                  (i) amend Williams' certificate of incorporation in a manner
           that changes any material term or provision of the Williams Common
           Stock;

                  (ii) materially amend Purchaser's certificate of
           incorporation;

                  (iii) engage in any material repurchase at a premium,
           recapitalization, restructuring or reorganization with respect to
           Williams' capital stock;

                  (iv) acquire in any manner any person or any business or
           division of any person, or otherwise acquire any assets, unless such
           acquisition or the entering into of a definitive agreement relating
           to or the consummation of such transaction would not (a) impose any
           material delay in the obtaining of, or materially increase the risk
           of not obtaining, any authorizations, consents, orders, declarations
           or approvals of any Governmental Entity (as defined in the Merger
           Agreement) necessary to consummate the Offer, the Merger or the
           expiration or termination of any applicable waiting period, (b)
           materially increase the risk of any Governmental Entity entering an
           order prohibiting the consummation of the Offer or the Merger or (c)
           increase the risk of not being able to remove any such order on
           appeal or otherwise; or

                  (v) enter into any contract or agreement to do any of the
           foregoing.

             Purchaser's Conduct of Business Pending the Merger.  Through the
      Effective Time, Purchaser will not engage in any activity of any nature
      except as provided in or contemplated by the Merger Agreement.

             Voting of Shares.  Williams has agreed to vote all Shares
      beneficially owned by it or its subsidiaries, including Purchaser, and
      including Shares purchased in the Offer, in favor of approval and adoption
      of the Merger.

      COVENANTS OF BARRETT RESOURCES.  Pursuant to the Merger Agreement, Barrett
Resources has agreed to comply with various covenants, including:

             Conduct of Business.  Prior to the earlier of (i) the Effective
      Time or (ii) such time as Williams' designees constitute a majority of the
      Board of Directors of Barrett Resources, Barrett Resources will, and will
      cause each of its subsidiaries to, except as contemplated by the Merger
      Agreement, carry on its business in the ordinary course. During such
      period, except as otherwise contemplated by the Merger Agreement, Barrett
      Resources will not, and will not permit any of its subsidiaries to, among
      other things, without the prior written consent of Williams (which consent
      shall not be unreasonably withheld or delayed):

                  (i) (a) pay any dividends on, or make any other distributions
           in respect of, any of its capital stock, except for dividends by a
           subsidiary of Barrett Resources to its parent or (b) split, combine
           or reclassify any of its capital stock or issue or authorize the
           issuance of any other securities in respect of, in lieu of or in
           substitution for shares of its capital stock;

                  (ii) issue, deliver, sell, pledge or otherwise encumber any
           shares of its capital stock, any other voting securities or any
           securities convertible into, or any rights, warrants or options to
           acquire, any such shares, voting securities or convertible
           securities, other than (a) the issuance of Shares upon exercise of
           Company Stock Options (as defined in the
                                        31
   41

           Merger Agreement) outstanding on the date hereof or (b) purchase,
           redeem or otherwise acquire any shares of capital stock of Barrett
           Resources or any of its subsidiaries or any other securities thereof
           or any rights, warrants or options to acquire any such shares or
           other securities;

                  (iii) amend its organizational documents;

                  (iv) except in accordance with certain pre-existing
           obligations, acquire, or agree to acquire any business or assets,
           other than transactions that are in the ordinary course of business,
           or which involve assets having a purchase price not in excess of $5
           million individually or $10 million in the aggregate;

                  (v) make or agree to make any new capital expenditure other
           than expenditures approved by the Board of Directors of Barrett
           Resources and within Barrett Resources' capital budget for fiscal
           2001; provided, however, that no individual capital expenditure
           pursuant to a single authority for expenditure may exceed $2.5
           million;

                  (vi) except in accordance with certain pre-existing
           obligations, sell, lease, license, encumber or otherwise dispose of,
           or agree to sell, lease, license, encumber or otherwise dispose of,
           any of its assets, other than transactions that are in the ordinary
           course of business or which involve assets having a current value not
           in excess of $1 million individually or $5 million in the aggregate;

                  (vii) except as required by applicable law or as provided in
           the Merger Agreement, materially alter the terms of employment of any
           director, officer or employee;

                  (viii) except as may be required as a result of a change in
           law or in generally accepted accounting principles, make any material
           change in its method of accounting;

                  (x) make any material Tax (as defined in the Merger Agreement)
           election (unless required by law) or enter into any settlement or
           compromise of any material Tax liability that could reasonably be
           expected to have a Material Adverse Effect on Barrett Resources;

                  (xi) except in the ordinary course of business consistent with
           past practice or pursuant to existing contracts or commitments (a)
           mortgage or otherwise encumber or subject to any Lien (as defined in
           the Merger Agreement) Barrett Resources' or its subsidiaries',
           properties or assets, or (b) license any of Barrett Resources'
           Intellectual Property (as defined in the Merger Agreement);

                  (xii) except in the ordinary course of business consistent
           with past practice and for certain liabilities set forth in the
           Merger Agreement, pay, discharge or satisfy any claims, liabilities
           or obligations;

                  (xii) (a) incur any Indebtedness (as defined in the Merger
           Agreement) or guarantee any Indebtedness or debt securities of
           another Person (as defined in the Merger Agreement), issue or sell
           any debt securities or warrants or other rights to acquire any debt
           securities of Barrett Resources or any of its subsidiaries, enter
           into any "Keep Well" or other agreement to maintain any financial
           statement condition of another Person or enter into any arrangement
           having the economic effect of any of the foregoing, except for
           borrowings incurred in the ordinary course of business (or to refund
           existing or maturing indebtedness) consistent with past practice and
           except for intercompany indebtedness between Barrett Resources and
           any of its wholly-owned subsidiaries or between such subsidiaries and
           except for Indebtedness, guarantees and similar commitments which do
           not exceed $10 million in the aggregate, or (b) make any loans,
           advances or capital contributions to, or investments in, any other
           Person, except in the ordinary course of business or pursuant to an
           agreement existing on the date hereof or loans, advances, capital
           contributions or investments which do not exceed $10 million in the
           aggregate; or

                                        32
   42

                  (xiii) enter into or authorize any contract, agreement or
           binding commitment to do any of the foregoing.

             Barrett Resources Shareholder Meeting and Shareholder
      Approval.  Barrett Resources will call and hold the Barrett Resources
      Special Meeting for the purpose of voting on the approval and adoption of
      the Merger Agreement and the Merger. Barrett Resources will use its
      reasonable best efforts to solicit proxies in favor of the Merger
      Agreement and the Merger and will take all other actions reasonably
      necessary to secure the vote or consent of stockholders to effect the
      Merger.

             No Solicitation; Acquisition Proposals.  Until the Effective Time
      or the termination of the Merger Agreement, (a) Barrett Resources will,
      and will cause its subsidiaries to, immediately cease and terminate any
      existing solicitation, initiation, knowing encouragement, discussion or
      negotiation with any Third Party (as defined in the Merger Agreement)
      conducted by Barrett Resources, its Subsidiaries or their respective
      representatives with respect to any Acquisition Proposal (as defined
      below) and (b) Barrett Resources will not, and Barrett Resources will
      cause and its subsidiaries' not to, directly or indirectly, (i) solicit,
      initiate or knowingly encourage, or knowingly take any other action to
      facilitate, any inquiries or the making or submission of any proposal that
      constitutes, or may reasonably be expected to lead to, any Acquisition
      Proposal; (ii) enter into any agreement with respect to any Acquisition
      Proposal or enter into any agreement requiring Barrett Resources to
      abandon, terminate or fail to consummate the acquisition of Shares; (iii)
      participate or engage in any discussions or negotiations with, or disclose
      or provide any non-public information relating to Barrett Resources or its
      subsidiaries to any Third Party relating to an Acquisition Proposal
      (except as required by legal process), or knowingly facilitate any effort
      to make an Acquisition Proposal or accept an Acquisition Proposal; or (iv)
      enter into any letter of intent, agreement or similar document relating to
      any Acquisition Proposal.

             Notwithstanding the immediately preceding paragraph, if, prior to
      the acquisition of Shares pursuant to the Offer, (a) Barrett Resources has
      received an unsolicited proposal from a Third Party relating to an
      Acquisition Proposal (under circumstances in which Barrett Resources has
      complied in all material respects with its obligations) and (b) the Board
      of Directors of Barrett Resources concludes in good faith (after
      consultation with a financial advisor, and on advice of counsel) (i) that
      such Acquisition Proposal may reasonably constitute a Superior Proposal
      (as defined below) and (ii) that the failure to provide such information
      or participate in such negotiations or discussions would result in a
      breach of its fiduciary duties, Barrett Resources may, subject to its
      giving Williams 24 hours prior written notice of the identity of such
      Third Party and, to the extent known, the terms and conditions of such
      Acquisition Proposal and of Barrett Resources intention to furnish
      nonpublic information to, or enter into discussions or negotiations with,
      such Third Party, (x) furnish information with respect to Barrett
      Resources and its subsidiaries to any Third Party pursuant to a customary
      confidentiality agreement containing terms not materially less restrictive
      than the terms of the Confidentiality Agreement between Barrett Resources
      and Williams and (y) participate in discussions or negotiations regarding
      such proposal or take certain actions described in the Merger Agreement.

             Barrett Resources shall within 24 hours notify and advise Williams
      of any Acquisition Proposal and the terms and conditions of such
      Acquisition Proposal. Barrett Resources will inform Williams on a prompt
      and current basis of the status of any discussions with a Third Party and,
      as promptly as practicable, of any change in the price, structure or form
      of the consideration or material terms of and conditions regarding such
      Acquisition Proposal.

             For purposes of the Merger Agreement, "Acquisition Proposal" means
      any inquiry, offer, proposal, indication of interest, signed agreement or
      completed action, as the case may be, by any Third Party which relates to
      a transaction or series of transactions involving Barrett Resources or the
      issuance or acquisition of 20% or more of the outstanding Shares or any
      tender or exchange offer that if consummated would result in any Person,
      together with all affiliates thereof, beneficially owning 20% or more of
      the outstanding Shares, or the acquisition, license, purchase or other

                                        33
   43

      disposition of a substantial portion of the business or assets of Barrett
      Resources outside the ordinary course of business.

             For purposes of the Merger Agreement, "Superior Proposal" means any
      bona fide written Acquisition Proposal (provided that for the purposes of
      this definition, the applicable percentages in the definition of
      Acquisition Proposal shall be fifty percent (50%) as opposed to twenty
      percent (20%)), on its most recently amended or modified terms, which the
      Board of Directors of Barrett Resources determines in its good faith
      judgment, (i) would, if consummated, result in a transaction that is more
      favorable to Barrett Resources' stockholders, from a financial point of
      view, than the transactions contemplated by the Merger Agreement and (ii)
      is reasonably capable of being completed.

             Modification to Recommendations.  Except as expressly permitted in
      Section 6.6 of the Merger Agreement, neither the Board of Directors of
      Barrett Resources nor any committee thereof will (i) withdraw, qualify,
      modify or amend, in a manner adverse to Williams, the Recommendations
      described above or make any public statement, filing or release
      inconsistent with such Recommendations (provided, however, that following
      the Barrett Resources Board of Directors' consideration and evaluation of
      an Acquisition Proposal, it is understood that for the purposes of the
      Merger Agreement, if Barrett Resources adopts a neutral position or no
      position with respect to the Acquisition Proposal, it will be considered
      an adverse modification of the Recommendations), (ii) approve or
      recommend, or propose publicly to approve or recommend, any Acquisition
      Proposal or (iii) cause Barrett Resources to enter into any acquisition
      agreement or other similar agreement related to any Acquisition Proposal
      (each, a "Subsequent Determination"), provided that if prior to the
      consummation of the Offer the Board of Directors of Barrett Resources
      determines in good faith (after it has received a Superior Proposal and
      after receipt of advice from its counsel) that the failure to make a
      Subsequent Determination would result in a breach by the Board of
      Directors of Barrett Resources of its fiduciary duties to its
      stockholders, the Board of Directors of Barrett Resources may inform
      Barrett Resources' stockholders that it no longer believes that the Offer
      and the Merger and the other transactions contemplated by the Merger
      Agreement are advisable, but only after 72 hours after delivery by Barrett
      Resources to Williams of a written notice (a "Subsequent Determination
      Notice") (i) advising Williams that the Board of Directors of Barrett
      Resources has received a Superior Proposal, (ii) specifying the terms and
      conditions of such Superior Proposal, (iii) identifying the person making
      such Superior Proposal and (iv) stating that Barrett Resources intends to
      make a Subsequent Determination. After providing such notice, Barrett
      Resources will provide a reasonable opportunity to Williams to make such
      adjustments in the terms and conditions of the Merger Agreement as would
      enable Barrett Resources to proceed with its Recommendations to its
      stockholders without a Subsequent Determination.

             Standstill Agreements.  Through the Effective Time, Barrett
      Resources will enforce and will not terminate, amend, modify or waive any
      standstill provision of any confidentiality or standstill agreement
      between Barrett Resources and other parties entered into prior to the date
      of the Merger Agreement in connection with the process to solicit
      acquisition proposals for Barrett Resources.

             Rights Plan.  Except as expressly required by the Merger Agreement
      or in order to delay the occurrence of a Distribution Date (as defined in
      the Barrett Resources Rights Agreement) in response to the public
      announcement of an Acquisition Proposal, Barrett Resources will not,
      without the prior written consent of Williams, amend the Barrett Resources
      Rights Agreement or take any other action with respect to, or make any
      determination under, the Barrett Resources Rights Agreement.

             Bank Debt.  Barrett Resources has agreed to use its reasonable best
      efforts to seek the consent of its bank lenders and the issuers of letters
      of credit to Barrett Resources to permit the consummation of the
      transactions contemplated by the Merger Agreement, without requiring
      repayment of Barrett Resources' indebtedness to such lenders or
      replacement of the letters of credit.

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   44

      MUTUAL COVENANTS.  Pursuant to the Merger Agreement, Barrett Resources,
Williams and Purchaser have agreed to comply with various mutual covenants,
including:

             Notice of Certain Matters.  Williams and Barrett Resources have
      agreed to notify each other promptly of any notices or communications
      received from any governmental or regulatory agency or authority in
      connection with the transactions contemplated by the Merger Agreement and
      of certain other events. Additionally, the parties will provide one
      another with copies of all filings made by them with any Governmental
      Entity in connection with the Merger Agreement and the transactions
      contemplated thereby.

             Preparation of Form S-4 and Proxy Statement/Prospectus.  Williams
      and Barrett Resources will, as soon as practicable following the
      acceptance of Shares pursuant to the Offer, prepare and Barrett Resources
      will file with the SEC a Proxy Statement (as defined in the Merger
      Agreement). Williams and Barrett Resources will also prepare and Williams
      will file with the SEC a registration statement on Form S-4 (the "Form
      S-4") for the offer and sale of the Williams Common Stock pursuant to the
      Merger. Barrett Resources and Williams will use all reasonable efforts to
      have the Form S-4 declared effective. Williams will also take any action
      (other than qualifying to do business in any jurisdiction in which it is
      not currently qualified or filing a general consent to service of process)
      required to be taken under any applicable state securities laws in
      connection with the issuance of Williams Common Stock in the Merger and
      Barrett Resources will furnish all information concerning itself and the
      holders of its capital stock as may be reasonably requested in connection
      with any such action and the preparation, filing and distribution of the
      Proxy Statement.

             Access.  Upon reasonable notice and subject to the Confidentiality
      Agreement between Barrett Resources and Williams, Barrett Resources and
      Williams will, and will cause their subsidiaries to, afford to the other
      party and its representatives reasonable access, during normal business
      hours to properties, books, contracts, commitments, records and
      representatives.

             Public Announcements.  Except as may be required by applicable law
      or a listing agreement with a securities exchange, Barrett Resources and
      Williams have agreed to consult with each other regarding the timing and
      content of any press release and public statements with respect to the
      Merger Agreement.

             Antitrust Filings.  Williams and Barrett Resources will (i)
      promptly make or cause to be made the filings required under the HSR Act
      and any other antitrust laws with respect to the Offer, the Merger and the
      other transactions contemplated by the Merger Agreement, (ii) comply at
      the earliest practicable date with any request under the HSR Act or such
      other antitrust laws for additional information, documents, or other, and
      (iii) cooperate with the other party in connection with any such filing
      and in connection with resolving any investigation or other inquiry of any
      governmental entity under any antitrust laws with respect to any such
      filing, the Offer, the Merger or such other transactions. Williams and
      Barrett Resources will promptly inform each other of any communication
      with, and any proposed understanding, undertaking, or agreement with, any
      governmental entity regarding any such filings, the Offer, the Merger or
      such other transactions.

      CONDITIONS TO THE MERGER.  The Merger Agreement provides that the
respective obligations of Williams, Purchaser and Barrett Resources to effect
the Merger will be subject to the fulfillment at or prior to the Effective Time
of the following conditions:

             (i) the Barrett Resources Stockholder Approval will have been
      obtained; provided, however that Williams and Purchaser will vote all of
      their Shares in favor of the Merger;

             (ii) no statute, rule, regulation, executive order, decree,
      temporary restraining order, preliminary or permanent injunction or other
      order issued by any court of competent jurisdiction or other Governmental
      Entity preventing the consummation of the Merger will be in effect;
      provided, however, that each of the parties will have used their
      reasonable best efforts to prevent the entry of any such temporary
      restraining order, injunction or other order and to appeal any injunction
      or other order that may be entered;
                                        35
   45

             (iii) Purchaser will have previously accepted for payment and paid
      for Shares pursuant to the Offer; provided, however, that this condition
      will be deemed satisfied if Williams or Purchaser fails to accept for
      payment and pay for Shares pursuant to the Offer in violation of the terms
      of the Merger Agreement and/or the Offer;

             (iv) the Form S-4 will have become effective under the Securities
      Act and will not be the subject of any stop order or proceedings seeking a
      stop order; and

             (v) the shares of Williams Common Stock to be issued in the Merger
      will have been approved for listing on the NYSE.

      TERMINATION.  The Merger Agreement may be terminated at any time prior to
the Effective Time:

             (i) by mutual written consent of Williams and Barrett Resources; or

             (ii) by either of Williams or Barrett Resources:

                  (a) if the Offer has expired or been terminated in accordance
           with the terms of the Merger Agreement without Williams or Purchaser
           having accepted for payment any Shares pursuant to the Offer, unless
           the failure to consummate the Offer is the result of a willful and
           material breach of the Merger Agreement by the party seeking to
           terminate the Merger Agreement; or

                  (b) if the Offer has not been consummated on or before August
           31, 2001, unless the failure to consummate the Offer is the result of
           a willful and material breach of the Merger Agreement by the party
           seeking to terminate the Merger Agreement; or

                  (c) if the Merger has not been consummated as a result of any
           Offer Conditions being incapable of being satisfied; or

                  (d) if any statute, rule, regulation, injunction or decree
           having the effects imposing certain specified material restrictions
           on the Offer or the Merger is in effect and has become final and
           nonappealable; or

             (iii) by Williams, if Barrett Resources has provided Williams with
      a Subsequent Determination Notice, or the Board of Directors of Barrett
      has made a Subsequent Determination or has modified its Recommendations in
      a manner adverse to Williams or has resolved to do any of the foregoing;
      or

             (iv) by Barrett Resources, if Barrett Resources makes a Subsequent
      Determination in compliance with the terms of the Merger Agreement,
      provided Barrett Resources has paid or concurrently pays Williams the sums
      required by the Merger Agreement; or

             (v) by Barrett Resources (a) if Purchaser or Williams has breached
      in any material respect any of their respective covenants, obligations or
      other agreements under the Merger Agreement, or (b) if the representations
      and warranties of Williams and Purchaser set forth in the Merger Agreement
      are not true and correct as of the date of the Merger Agreement and as of
      the expiration of the date of termination of the Merger Agreement, except
      to the extent expressly made as of an earlier date, in which case as of
      such date (subject to limitations regarding the materiality of such
      breach); provided, that the breach of the covenant, obligation, agreement,
      representation or warranty is incapable of being or has not been cured by
      Williams or Purchaser within 10 calendar days following written notice by
      Barrett Resources to Williams of such breach or failure to perform; or

             (vi) by Williams (a) if Barrett Resources has breached in any
      material respect any of its covenants, obligations or other agreements
      under the Agreement, or (b) if Barrett Resources' representations and
      warranties in the Merger Agreement are not true and correct as of the date
      of the Merger Agreement and as of the expiration of the date of
      termination of the Merger Agreement, except to the extent expressly made
      as of an earlier date, in which case as of such date

                                        36
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      (subject to limitations regarding the materiality of such breach);
      provided, that the breach of the covenant, obligation, agreement,
      representation or warranty is incapable of being or has not been cured by
      Barrett Resources within 10 calendar days following written notice by
      Williams to Barrett Resources of such breach or failure to perform.

      EMPLOYEE BENEFITS.  The Merger Agreement provides that employees of
Barrett Resources and its subsidiaries will remain employed immediately
following the consummation of the Merger, generally will receive credit for
co-payments, deductible, unused vacation and unused sick leave and generally
will receive service credit for purposes of eligibility and vesting under each
benefit plan (and for purposes of determination of benefits under certain
benefit plans) in which they are eligible to participate following consummation
of the Offer. With respect to welfare plans, Williams generally will waive or
cause to be waived limitations as to pre-existing conditions exclusions and
waiting periods with respect to such employees. Williams will honor or cause to
be honored all employment agreements, bonus agreements, severance agreements,
severance plans and non-competition agreements with the directors, officers and
employees of Barrett Resources and its subsidiaries.

      OPTIONS.  The Merger Agreement provides that, subject to certain
exceptions described below, each option to acquire Barrett Resources common
stock (a "Barrett Resources Stock Option") that is outstanding immediately prior
to the consummation of the Offer (the "Offer Consummation Date") will vest and
become fully exercisable at such time. On the Offer Consummation Date (with
respect to Barrett Resources Stock Options held by persons who are not subject
to the reporting requirements of Section 16(a) of the Exchange Act) and at the
Effective Time (with respect to Barrett Resources Stock Options held by persons
who are subject to the reporting requirements of Section 16(a) of the Exchange
Act), each Barrett Resources Stock Option will be adjusted to represent an
option to purchase the number of shares of Barrett Resources common stock (a
"Barrett Resources Adjusted Option") (rounded down to the nearest full share)
determined by multiplying (i) the number of shares of Barrett Resources Common
Stock subject to such Barrett Resources Stock Option immediately prior to the
Offer Consummation Date (with respect to Barrett Resources Stock Options held by
persons who are not subject to the reporting requirements of Section 16(a) of
the Exchange Act) and immediately prior to the Effective Time (with respect to
Barrett Resources Stock Options held by persons who are subject to the reporting
requirements of Section 16(a) of the Exchange Act) by (ii) 0.5, at an exercise
price per share of Barrett Resources common stock equal to the exercise price
per share of Barrett Resources common stock immediately prior to the Offer
Consummation Date.

      In addition, promptly following the Offer Consummation Date (with respect
to holders of Barrett Resources Stock Options who are not subject to the
reporting requirements of Section 16(a) of the Exchange Act), and promptly
following the Effective Time (with respect to holders of Barrett Resources Stock
Options who are subject to the reporting requirements of Section 16(a) of the
Exchange Act), Williams will pay to the holder of each Barrett Resources Stock
Option an amount of cash (rounded up to the nearest cent) equal to the product
of (A) (x) $73.00 minus (y) the exercise price per share of Barrett Resources
common stock immediately prior to the Offer Consummation Date and (B) the number
of shares of Barrett Resources common stock subject to such option multiplied by
0.5 (rounded up to the nearest full share).

      At the Effective Time, each Barrett Resources Adjusted Option will be
assumed by Williams and become and represent an option to purchase the number of
Williams Common Stock (rounded to the nearest full share, or if there is not be
a nearest share, the next greater full share) determined by multiplying (i) the
number of shares of Barrett Resources Common Stock subject to such Barrett
Resources Adjusted Option immediately prior to the Effective Time by (ii) 1.767,
at an exercise price per share of Williams Common Stock (rounded up to the
nearest tenth of a cent) equal to (A) the exercise price per share of Barrett
Resources common stock immediately prior to the Effective Time divided by 1.767.
Each Barrett Resources Adjusted Option so converted will be exercisable upon the
same terms and conditions as under the applicable plan under which it was
granted and the applicable option agreement issued thereunder, except as
otherwise provided in the Merger Agreement.

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   47

      At the Effective Time, Williams will assume the Barrett Resources stock
plans, with the result that all obligations of Barrett Resources under the
Barrett Resources stock plans, including with respect to Barrett Resources
Adjusted Options outstanding at the Effective Time, will be obligations of
Williams following the Effective Time.

      The Merger Agreement provides that, notwithstanding anything in the
foregoing to the contrary, to the extent an option holder holds any
unexercisable incentive stock options ("Unvested ISOs") on the Offer
Consummation Date that do not become exercisable upon consummation of the Offer
pursuant to the terms of the option plan under which they were granted, then, to
the extent possible, each such Unvested ISO will be converted into the right to
receive cash in full and the other options held by such option holder will be
appropriately adjusted so that the aggregate amount of cash payable to such
option holder in respect of all of his or her Barrett Resources Stock Options
pursuant to the terms of the Merger Agreement is not increased because of the
treatment of Unvested ISOs under the Merger Agreement.

      STAY BONUSES; SEVERANCE.  Prior to the Effective Time, Barrett Resources
will be permitted to award bonuses to employees of Barrett Resources or any of
its subsidiaries in an aggregate amount not to exceed $2,000,000, with such
bonuses to be allocated at the direction of its Chief Executive Officer with the
consent of Williams, which consent will not be unreasonably withheld or delayed.
Such bonuses will be paid upon the earlier of 90 days following the Effective
Time and 30 days following the termination of the Merger Agreement (the "Payment
Date") to each employee to whom such a bonus has been awarded and who continues
to be employed by Barrett Resources (or any successor or affiliate of Barrett
Resources) on the Payment Date or whose employment terminates prior to the
Payment Date due to death, Disability, termination by Barrett Resources (or any
successor or affiliate of Barrett Resources) without Cause, or termination by
the employee with Good Reason (as such capitalized terms are defined in Barrett
Resources' Severance Protection Plan). However, no such bonus will be paid to
any employee who has entered into a Severance Protection Agreement with Barrett
Resources and whose employment terminates prior to the Payment Date entitling
such employee to a severance payment pursuant to Section 3.1(b) of such
Severance Protection Agreement.

      Williams will maintain or cause to be maintained the Barrett Resources
severance policy as in effect on the date of the Merger Agreement or will
replace such policy with a policy providing equal or more favorable
compensation, for a period of at least two years from the Effective Time. Each
employee of Barrett Resources or any of its subsidiaries whose employment is
terminated upon, or within 18 months following, the consummation of the Offer,
other than an employee who has entered into a Severance Protection Agreement
with Barrett Resources, will receive a cash payment from Barrett Resources or
Williams in the amount of $8,000 which may, in the sole discretion of such
employee, be used to obtain outplacement services, to assist in the transition
to subsequent employment or for any other purpose.

      TAX TREATMENT.  The Merger Agreement is intended to constitute a "plan of
reorganization" with respect to the Offer and the Forward Merger for United
States federal income tax purposes. From and after the date of the Merger
Agreement, each party is required to use its reasonable best efforts to cause
the Offer and the Forward Merger to qualify, and may not, without prior written
consent, knowingly take any actions, or cause any actions to be taken, which
could reasonably be expected to prevent the Offer and the Forward Merger from
qualifying as a reorganization.

      BOARD OF DIRECTORS.  Subject to compliance with Section 14(f) of the
Exchange Act, promptly after Purchaser purchases Shares pursuant to the Offer
(subject to the satisfaction of the Minimum Condition), Purchaser will be
entitled to designate up to the number of directors, rounded to the nearest
whole number, of Barrett Resources' Board of Directors, as will make the
percentage of Barrett Resources' directors designated by Purchaser equal to the
aggregate voting power of the shares of Barrett Resources Common Stock held by
Williams or any of its subsidiaries. However, in the event that Purchaser's
designees are elected to the Board of Directors of Barrett Resources, until the
Effective Time, such Board of Directors will have at least two directors who are
directors on the date of the Merger Agreement and who are not officers of
Barrett Resources (the "Independent Directors"). If the number of Independent
Directors is reduced below two for any reason whatsoever, the remaining
Independent Directors will

                                        38
   48

designate a person to fill such vacancy who will be deemed to be an Independent
Director or, if no Independent Directors then remain, the other directors will
designate two persons to fill such vacancies who will not be officers or
affiliates of Barrett Resources, Williams or any of their subsidiaries.

      Following the election or appointment of Purchaser's designees, a
concurrence will be required of a majority of the Independent Directors for (a)
any amendment, or waiver of any term or condition, of the Merger Agreement or
the Restated Certificate of Incorporation or Bylaws of Barrett Resources and (b)
any termination of the Merger Agreement by Barrett Resources, any extension by
Barrett Resources of the time for the performance of any of the obligations or
other acts of Purchaser or waiver or assertion of any of Barrett Resources'
rights under the Merger Agreement, and any other consent or action by Barrett
Resources' Board of Directors with respect to the Merger Agreement. As a result
of the purchase of Shares by Purchaser pursuant to the Offer, it is contemplated
that Purchaser's designees will represent at least one-half of Barrett
Resources' Board of Directors after the purchase of Shares until the Effective
Time.

      INDEMNIFICATION.  Williams will, or will cause the Surviving Corporation
to, honor for a period of not less than six years from the Effective Time (or,
for matters occurring at or prior to the Effective Time that have not been
resolved, until such matters are finally resolved), all rights to
indemnification or exculpation, existing in favor of a director, officer,
employee or agent (an "Indemnified Person") of Barrett Resources or any of its
subsidiaries relating to actions or events through the Effective Time. The
Surviving Corporation, however, will not be required to indemnify any
Indemnified Person for any proceeding to the extent involving any claim
initiated by such Indemnified Person unless such proceeding was authorized by
the Board of Directors of Barrett Resources or was brought to enforce rights
under this Merger Agreement. In the event that any Indemnified Person becomes
involved in any actual or threatened action, suit, claim, proceeding or
investigation after the Effective Time, Williams will, or will cause the
Surviving Corporation to, promptly advance to such Indemnified Person his or her
expenses, subject to such Indemnified Person undertaking to reimburse all
advances amounts in the event of a non-appealable determination that such
Indemnified Person is not entitled thereto.

      DIRECTORS AND OFFICERS INSURANCE.  Prior to the Effective Time, Barrett
Resources will have the right to obtain and pay for in full a "tail" coverage
directors' and officers' liability insurance policy ("D&O Insurance") covering a
period of at least six years after the Effective Time. If Barrett Resources is
unable to obtain such insurance, the Surviving Corporation will maintain Barrett
Resources' D&O Insurance for a period of at least six years after the Effective
Time. However, the Surviving Corporation may substitute policies of similar
coverage and amounts with terms no less advantageous. Nevertheless, Barrett
Resources will not, without Williams' consent, expend in excess of 300% of the
last annual premium paid to procure the coverage and neither Williams nor the
Surviving Corporation will be required to expend in excess of 300% of the last
annual premium paid.

      FEES AND EXPENSES.  If the Offer has not been accepted, Barrett Resources
will pay Williams a fee equal to $75.5 million as a result of the occurrence of
any of the following events (each of which is a "Trigger Event"):

             (i) Barrett Resources has received an Acquisition Proposal (other
      than the cash tender offer by SRM Acquisition Corp. (an affiliate of
      Shell), pursuant to the Shell Offer, dated March 12, 2001, as amended to
      the date of the Merger Agreement, at a purchase price of $60 per Share, it
      being understood that Barrett Resources will be deemed to have received an
      Acquisition Proposal (x) if SRM Acquisition Company amends its tender
      offer by increasing its tender offer price above $60 per Share, or (y) if
      an acquisition proposal other than the Shell Offer is made by any other
      affiliate of Shell) after the date of the Merger Agreement (but prior to
      the termination of the Merger Agreement), and at any time prior to, or
      within 12 months after, the termination of the Merger Agreement (unless
      terminated without the fault of any party or due to Williams' or
      Purchaser's default), or Barrett Resources has entered into, or has
      publicly announced its intention to enter into, an agreement or an
      agreement in principle with respect to any Acquisition Proposal;

                                        39
   49

             (ii) Barrett Resources has provided Williams with a Subsequent
      Determination Notice or the Board of Directors of Barrett Resources (or
      any committee thereof) (a) has made a Subsequent Determination, (b) has
      included in the Schedule 14D-9 its Recommendations with modification or
      qualification in a manner adverse to Williams, or (c) has resolved to, or
      publicly announced an intention to, take any of the actions as specified
      in the Merger Agreement; or

             (iii) (a) as of the final expiration date of the Offer, all
      conditions to the consummation of the Offer have been met or waived except
      for satisfaction of the Minimum Condition, (b) there has been made
      subsequent to the date of the Merger Agreement (but before such expiration
      date of the Offer) an Acquisition Proposal (other than the cash tender
      offer by SRM Acquisition Corp, it being understood that Barrett Resources
      will be deemed to have received an Acquisition Proposal (x) if SRM
      Acquisition Company amends its tender offer by increasing its tender offer
      price above $60 per Share, or (y) if an Acquisition Proposal other than
      the Shell Offer is made by any other affiliate of Shell) and (c) at any
      time prior to, or within 12 months after, the expiration or termination of
      the Offer, Barrett Resources has entered into, or has publicly announced
      its intention to enter into, an agreement or agreements in principle with
      respect to any Acquisition Proposal.

             Except as otherwise specified above, all fees and expenses incurred
      in connection with the Offer and the Merger, the Merger Agreement and the
      transactions contemplated by the Merger Agreement will be paid by the
      party incurring such fees or expenses, whether or not the Offer or the
      Merger is consummated:

                  (i) provided, that if the Merger Agreement is terminated as a
           result of the occurrence of a Trigger Event, Barrett Resources will
           also reimburse Williams for all out-of-pocket fees payable and
           expenses reasonably incurred by Williams up to a maximum of $15
           million.

                  (ii) provided, that if Barrett Resources has breached or
           failed to perform in any material respect any of its representations,
           warranties, covenants or other agreements contained in the Merger
           Agreement, which breach or failure to perform (A) would cause Barrett
           Resources to breach or fail to perform any of its covenants,
           obligations or agreements under the Merger Agreement, or cause any of
           the representations and warranties of Barrett Resources that are not
           qualified as to materiality not to be true and correct, and (B) is
           incapable of being or has not been cured by Barrett Resources prior
           to or on the earlier of (x) ten days immediately following written
           notice by Williams to Barrett Resources of such breach or failure to
           perform and (y) the expiration or termination of the Offer in
           accordance with the terms of the Merger Agreement Barrett Resources
           will reimburse Williams for all out-of-pocket fees payable and
           expenses reasonably incurred by Williams up to a maximum of $15
           million.

                  (iii) provided, that if Barrett Resources has terminated the
           Merger Agreement as a result of the breach by Williams or Purchaser
           of any material representation, warranty, covenant or other agreement
           under the Merger Agreement, and such breach of a representation,
           warranty, covenant or other agreement is incapable of being or has
           not been cured by Williams within 10 calendar days following written
           notice of such breach or failure to perform, Williams will reimburse
           Barrett Resources for all out-of-pocket fees payable and expenses
           reasonably incurred by Barrett Resources up to a maximum of $15
           million.

      AMENDMENTS.  Subject to certain customary restrictions, including, among
other things, a restriction on Purchaser's right to waive the Minimum Condition,
the Merger Agreement may be amended at any time, but after the Barrett Resources
Stockholder Approval has been obtained, no amendment which requires approval by
Barrett Resources' stockholders will be made without obtaining such approval.

      GOVERNING LAW.  The Merger Agreement is governed by, and construed in
accordance with Delaware law, regardless of the laws that might otherwise govern
under applicable principles of conflicts of laws thereof.

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   50

  Effects of Inability to Consummate the Merger

      If each of the Offer and the Merger is consummated, stockholders of
Barrett Resources who elected not to tender their Shares in the Offer, or had
fewer Shares accepted than tendered in the Offer as a result of proration, will
have each of those Shares that they continue to hold following consummation of
the Offer converted in the Merger into 1.767 shares of Williams Common Stock.

      If, following the consummation of the Offer, the Merger is not
consummated, Purchaser will control the number of Shares purchased by it in the
Offer. Under the Merger Agreement, subject to satisfaction of the Minimum
Condition, Purchaser will be entitled to representation on the Barrett Resources
Board of Directors in the same proportion as the number of Shares then
beneficially owned by Purchaser bears to the total number of Shares outstanding,
rounded up to the nearest whole number. As a result of its ownership of such
Shares and its representation on the Barrett Resources Board, Purchaser may be
able to influence and potentially control decisions of the Barrett Resources
Board of Directors.

      Following consummation of the Offer (including if the Merger is not
consummated), Williams and Purchaser reserve the right to acquire additional
Shares through private purchases, market transactions, tender or exchange offers
or otherwise on terms and at prices that may be more or less favorable than
those of the Offer or, subject to any applicable legal restrictions, to dispose
of any or all Shares acquired by Purchaser and Williams.

  Statutory Requirements

      In general, under the DGCL a merger of two Delaware corporations requires
the adoption of a resolution by the board of directors of each of the
corporations desiring to merge approving an agreement of merger containing
provisions with respect to certain statutorily specified matters and the
approval of such agreement of merger by the stockholders of each corporation by
the affirmative vote of the holders of a majority of all the outstanding shares
of stock entitled to vote on such merger. The respective Boards of Directors of
Williams, Purchaser and Barrett Resources have each approved the Merger
Agreement and the Merger.

      The Merger Agreement and the Merger are subject to the Barrett Resources
Stockholder Approval.

  Appraisal Rights

      No appraisal rights are available in connection with the Offer or the
Merger.

  Plans for Barrett Resources

      Williams and Purchaser intend to conduct a review of Barrett Resources and
its subsidiaries and their respective assets, businesses, corporate structure,
capitalization, operations, properties, policies, management and personnel.
Based on this review, Williams and Purchaser may take actions or make changes
that they consider desirable and reserve the right to effect such actions or
changes. Williams' and Purchaser's decisions could be affected by information
hereafter obtained, changes in general economic or market conditions or in the
business of Barrett Resources or its subsidiaries, actions by Barrett Resources
or its subsidiaries and other factors.

      Williams currently anticipates that Barrett Resources' principal offices
in Denver, Colorado will serve as the Rocky Mountain principal offices for
Williams' oil and gas exploration operations after the consummation of the
Merger.

      Except as described in this Section 11 or elsewhere in this Offer to
Purchase, Barrett Resources has no present plans or proposals that would relate
to or would result in (a) an extraordinary corporate transaction, such as a
merger, reorganization or liquidation, involving Barrett Resources or any of its
subsidiaries, (b) a purchase, sale or transfer of a material amount of assets of
Barrett Resources or any of its subsidiaries, (c) any change in the present
Board of Directors or management of Barrett Resources, (d) any material change
in the present capitalization or dividend policy of Barrett Resources, (e) any
material change in Barrett Resources' corporate structure or business, (f)
causing a class of securities of Barrett Resources to be delisted from a
national securities exchange or to cease to be authorized to be quoted in an
inter-dealer quotation system of a registered national securities association or
(g) a class of
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   51

equity securities of Barrett Resources becoming eligible for termination of
registration pursuant to Section 12(g)(4) of the Exchange Act.

  Confidentiality Agreements.

      On March 9, 2001, Williams signed the Confidentiality Agreement which
provides that, subject to the terms of the Confidentiality Agreement, Williams
will keep confidential certain nonpublic information furnished by Barrett
Resources. In addition, subject to the terms of the Confidentiality Agreement,
Williams agreed not to, among other things, (i) acquire any assets, businesses
or securities of Barrett Resources, (ii) solicit proxies or consents with regard
to Barrett Resources or (iii) otherwise seek control of Barrett Resources, in
each case without the consent of Barrett Resources, until the close of business
on May 11, 2001. A copy of the Confidentiality Agreement is filed as Exhibit
(d)(2) hereto and is incorporated herein by reference. The foregoing description
of the Confidentiality Agreement is qualified in its entirety by reference to
such Exhibit.

      In connection with its due diligence review of Williams, on May 6, 2001,
Barrett Resources signed a nondisclosure agreement (the "Nondisclosure
Agreement") providing that, among other things subject to the terms of the
Nondisclosure Agreement, Barrett Resources will keep confidential certain
nonpublic information furnished by Williams. A copy of the Nondisclosure
Agreement is filed as Exhibit (d)(3) hereto and is incorporated herein by
reference. The foregoing description of the Nondisclosure Agreement is qualified
in its entirety by reference to such Exhibit.

  "Going Private" Transactions

      The SEC has adopted Rule 13e-3 under the Exchange Act which is applicable
to certain "going private" transactions and which may under certain
circumstances be applicable to the Merger. However, Rule 13e-3 would be
inapplicable to the Merger because holders of Shares will receive only shares of
Williams Common Stock in the Merger (exclusive of cash in lieu of fractional
shares), and the Williams Common Stock is registered under Section 12 of the
Securities Act and is listed on the NYSE. If applicable, Rule 13e-3 would
require, among other things, that certain financial information concerning the
fairness of the proposed transaction and the consideration offered to minority
stockholders in such transaction be filed with the SEC and disclosed to
stockholders prior to the consummation of the transaction.

12. SOURCE AND AMOUNT OF FUNDS.

      Purchaser estimates that the total amount of funds required to purchase
16,730,502 Shares pursuant to the Offer and to pay related fees and expenses
will be approximately $1.23 billion. In addition, Barrett Resources has agreed
in the Merger Agreement to seek the consent of its bank lenders under its credit
agreement to permit it to consummate the transactions contemplated by the Merger
Agreement without repaying the indebtedness under the credit agreement. If such
bank consents are not obtained, Williams would need approximately an additional
$145 million to repay the indebtedness under the credit agreement (the
"Refinancing"). Purchaser intends to fund the purchase of Shares pursuant to the
Offer and the Refinancing, if required, from capital contributions by Williams.
Williams currently has sufficient liquidity available through the unused portion
of its existing commercial paper program and revolving credit agreements to make
such capital contributions to Purchaser. In addition, Williams may choose to
establish a bridge loan facility to fund all or part of such capital
contributions. Finally, Williams may choose to review other funding options such
as volumetric production payments, convertible debt or equity or other
structured alternatives in order to make the required capital contributions to
Purchaser.

      Williams' commercial paper program involves the private placement of
unsecured, commercial paper notes with maturities of up to 270 days. The
commercial paper generally has an effective interest rate approximating the then
market rate of interest for commercial paper of similar rating, currently
approximately 5.28%. Williams may refinance any commercial paper borrowings used
to finance the purchase of Shares pursuant to the Offer and the Refinancing, if
any, through private placements of additional commercial paper, borrowings under
its credit agreements or, depending on market or business conditions, through
such other financing as Williams may deem appropriate.

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   52

13. DIVIDENDS AND DISTRIBUTIONS.

      If on or after the date of the Merger Agreement, Barrett Resources (a)
splits, combines or otherwise changes the Shares or its capitalization, (b)
acquires Shares or otherwise causes a reduction in the number of Shares, (c)
issues or sells additional Shares (other than the issuance of Shares reserved
for issuance as of the date of the Merger Agreement under option and employee
stock purchase plans in accordance with their terms as publicly disclosed as of
the date of the Merger Agreement) or any shares of any other class of capital
stock, other voting securities or any securities convertible into or
exchangeable for, or rights, warrants or options, conditional or otherwise, to
acquire, any of the foregoing or (d) discloses that it has taken such action,
then, without prejudice to Williams' and Purchaser's rights under Section 14 of
this document, Williams and Purchaser, in their sole discretion, may make such
adjustments in the purchase price and other terms of the Offer as they deem
appropriate to reflect such split, combination or other change or action,
including, without limitation, the Minimum Condition or the number or type of
securities offered to be purchased. Barrett Resources has agreed in the Merger
Agreement not to take any of the foregoing actions without Williams' consent.

      If on or after the date of the Merger Agreement, Barrett Resources
declares or pays any dividend on the Shares or any distribution (including,
without limitation, the issuance of additional Shares pursuant to a stock
dividend or stock split, the issuance of other securities or the issuance of
rights for the purchase of any securities) with respect to the Shares that is
payable or distributable to stockholders of record on a date prior to the
transfer into the name of Purchaser or its nominees or transferees on Barrett
Resources' stock transfer records of the Shares purchased pursuant to the Offer,
and if Shares are purchased in the Offer, then, without prejudice to Purchaser's
rights under Section 14 of this document, (a) the purchase price per Share
payable by Purchaser pursuant to the Offer shall be reduced by the amount of any
such cash dividend or cash distribution and (b) any such non-cash dividend,
distribution, issuance, proceeds or rights to be received by the tendering
stockholders will (i) be received and held by the tendering stockholders for the
account of Purchaser and will be required to be promptly remitted and
transferred by each tendering stockholder to the Depositary for the account of
Purchaser, accompanied by appropriate documentation of transfer or (ii) at the
direction of Purchaser, be exercised for the benefit of Purchaser, in which case
the proceeds of such exercise will promptly be remitted to Purchaser. Pending
such remittance and subject to applicable law, Purchaser will be entitled to all
rights and privileges as owner of any such non-cash dividend, distribution,
issuance, proceeds or rights and may withhold the entire purchase price or
deduct from the purchase price the amount or value thereof, as determined by
Purchaser in its sole discretion. Barrett Resources has agreed in the Merger
Agreement not to take any of the foregoing actions without Williams' consent.

14. CONDITIONS OF THE OFFER.

      Notwithstanding any other provision of the Offer, subject to the terms of
the Merger Agreement, Purchaser shall not be required to accept for payment or
pay for (subject to any applicable rules and regulations of the SEC, including
Rule 14e-1(c) under the Exchange Act (relating to Purchaser's obligation to pay
for or return tendered Shares after the termination or withdrawal of the Offer))
any Shares tendered, if by the expiration of the Offer (as it may be extended in
accordance with the requirements of the Merger Agreement), (1) there shall not
have been validly tendered and not withdrawn CONDITIONS OF THE OFFER.

      Notwithstanding any other provision of the Offer, subject to the terms of
the Merger Agreement, Purchaser shall not be required to accept for payment or
pay for (subject to any applicable rules and regulations of the SEC, including
Rule 14e-1(c) under the Exchange Act (relating to Purchaser's obligation to pay
for or return tendered Shares after the termination or withdrawal of the Offer))
any Shares tendered, if by the expiration of the Offer (as it may be extended in
accordance with the requirements of the Merger Agreement), (1) there shall not
have been validly tendered and not withdrawn prior to the expiration of the
Offer 16,730,502 Shares, (2) the applicable waiting period under the HSR Act and
any other applicable antitrust laws shall not have expired or been terminated,
or (3) at any time

                                        43
   53

on or after the date of the Merger Agreement and prior to the acceptance for
payment of Shares pursuant to the Offer, any of the following conditions exist:

             (i) there shall be instituted or pending any action or proceeding
      by any Governmental Entity:

                  (a) challenging or seeking to make illegal, to delay
           materially or otherwise directly or indirectly to restrain or
           prohibit the making of the Offer or the Merger, the acceptance for
           payment of, or the payment for, some of or all the Shares by Williams
           or Purchaser or the consummation by Williams or Purchaser of the
           Merger or seeking to obtain material damages,

                  (b) seeking to restrain or prohibit Williams' or Purchaser's
           ownership or operation (or that of their respective subsidiaries or
           affiliates) of all or any material portion of the business or assets
           of Barrett Resources and its subsidiaries, taken as a whole, or of
           Williams and its subsidiaries, taken as a whole, or to compel
           Williams or any of its subsidiaries or affiliates to dispose of or
           hold separate all or any material portion of the business or assets
           of Barrett Resources and its subsidiaries, taken as a whole, or of
           Williams and its subsidiaries, taken as a whole,

                  (c) seeking to impose material limitations on the ability of
           Williams or any of its subsidiaries effectively to exercise full
           rights of ownership of the Shares, including, without limitation, the
           right to vote any Shares acquired or owned by Williams or any of its
           subsidiaries or affiliates on all matters properly presented to
           Barrett Resources' stockholders, or

                  (d) seeking to require divestiture by Williams or any of its
           subsidiaries of any Shares; or

             (ii) there shall be any action taken, or any statute, rule,
      regulation, injunction, order or decree enacted, enforced, promulgated,
      issued or deemed applicable to the Merger Agreement, the Offer or the
      Merger, by any governmental entity that is reasonably likely, directly or
      indirectly, to result in any of the consequences referred to in clauses
      (a) through (d) of paragraph (i) above, subject thereto; or

             (iii) Barrett Resources shall have breached or failed to perform in
      any material respect any of its covenants, obligations or agreements under
      the Merger Agreement; or

             (iv) the representations and warranties of Barrett Resources set
      forth in the Merger Agreement that are qualified as to materiality shall
      not be true and correct as of the date of the Merger Agreement and as of
      the expiration of the Offer (including any extension thereof) (except to
      the extent expressly made as of an earlier date, in which case as of such
      earlier date), or any of the representations and warranties set forth in
      the Merger Agreement that are not so qualified as to materiality shall not
      be true and correct in any material respect as of the date of the Merger
      Agreement and as of the expiration of the Offer (except to the extent
      expressly made as of an earlier date, in which case as of such earlier
      date); provided that this condition shall not be deemed to exist unless
      any such breaches of representation or warranty (without regard to any
      "Materiality" or "Material Adverse Effect" or similar qualifier or
      threshold), individually or in the aggregate, has had or could reasonably
      be expected to have, a Material Adverse Effect (as defined in the Merger
      Agreement) on Barrett Resources; or

             (v) the Merger Agreement shall have been terminated in accordance
      with its terms; or

             (vi) the Board of Directors of Barrett Resources (or any committee
      thereof) shall have made a Subsequent Determination (as defined in the
      Merger Agreement) with respect to an Acquisition Proposal (as defined in
      the Merger Agreement);

which, in the good faith judgment of Williams, in any such case, makes it
inadvisable to proceed with acceptance for payment, or payment for, Shares in
the Offer.

                                        44
   54

      The foregoing conditions are for the sole benefit of Williams and
Purchaser and may, subject to the terms of the Merger Agreement, be waived by
Williams and Purchaser in their reasonable discretion in whole at any time or in
part from time to time. The failure by Williams or Purchaser at any time to
exercise its rights under any of the foregoing conditions shall not be deemed a
waiver of any such right; the waiver of any such right with respect to
particular facts and circumstances shall not be deemed a waiver with respect to
any other facts and circumstances, and each such right shall be deemed an
ongoing right which may be asserted at any time or from time to time.

      A public announcement may be made of a material change in, or waiver of,
such conditions and the Offer may, in certain circumstances, be extended in
connection with any such change or waiver. Purchaser may not waive the Minimum
Condition without the written consent of Barrett Resources.

      Purchaser acknowledges that the SEC believes that (a) if Purchaser is
delayed in accepting the Shares it must either extend the Offer or terminate the
Offer and promptly return the Shares and (b) the circumstances in which a delay
in payment is permitted are limited and do not include unsatisfied conditions of
the Offer, except with respect to most required regulatory approvals.

15. LEGAL MATTERS; REQUIRED REGULATORY APPROVALS.

      GENERAL.  Based upon an examination of publicly available information with
respect to Barrett Resources and the representations and warranties of Barrett
Resources contained in the Merger Agreement, neither Purchaser nor Williams is
aware of any license or other regulatory permit that is material to the business
of Barrett Resources and its subsidiaries, taken as a whole, which might be
adversely affected by the acquisition of Shares by Purchaser pursuant to the
Offer or the Merger, or, except as set forth below, of any approval or other
action by any domestic (federal or state) or foreign governmental,
administrative or regulatory authority or agency which would be required prior
to the acquisition of Shares by Purchaser pursuant to the Offer or the Merger.
Should any such approval or other action be required, it is Purchaser's and
Williams' present intention to seek such approval or action. Purchaser does not
currently intend, however, to delay the purchase of Shares tendered pursuant to
the Offer pending the outcome of any such action or the receipt of any such
approval. There is no assurance (i) that any such approval or other action, if
needed, would be obtained without substantial conditions, (ii) that adverse
consequences might not result to the business of Barrett Resources, Purchaser or
Williams, (iii) that certain parts of the businesses of Barrett Resources,
Purchaser or Williams might not have to be disposed of or held separate or (iv)
that other substantial conditions complied with in order to obtain such approval
or other action or in the event that such approval was not obtained or such
other action was not taken. Purchaser's obligation under the Offer to accept for
payment and pay for Shares is subject to certain conditions, including
conditions relating to the legal matters discussed in this Section 15. See
Section 14, "Conditions of the Offer."

      STATE TAKEOVER LAWS.  A number of states throughout the United States have
enacted takeover statutes that purport, in varying degrees, to be applicable to
attempts to acquire securities of corporations that are incorporated or have
assets, stockholders, executive offices or places of business in those states.
In 1982, in Edgar v. MITE Corp., the Supreme Court of the United States held
that the Illinois Business Takeover Act, which involved state securities laws
that made the takeover of certain corporations more difficult, imposed a
substantial burden on interstate commerce and was therefore unconstitutional.
However, in 1987, in CTS Corp. v. Dynamics Corp. of America, the Supreme Court
of the United States held that a state may, as a matter of corporate law and, in
particular, those laws concerning corporate governance, constitutionally
disqualify a potential acquirer from voting on the affairs of a target
corporation without prior approval of the remaining stockholders; provided that
the laws were applicable only under certain conditions.

      Section 203 of the DGCL limits the ability of a Delaware corporation to
engage in business combinations with "interested stockholders" (defined
generally as any person that directly or indirectly beneficially owns 15% or
more of the outstanding voting stock of the subject corporation) for three years
following the date such person became an "interested stockholder," unless, among
other things, the board of directors of the subject corporation has given its
prior approval of either the transaction in which such

                                        45
   55

person became an interested stockholder or the business combination. Barrett
Resources has represented in the Merger Agreement that it approved the Merger
Agreement and the transactions contemplated thereby, including the Offer and the
Merger, and has taken all appropriate action so that neither Williams nor
Purchaser will be an "interested stockholder" within the meaning of Section 203
of the DGCL by virtue of Williams, Purchaser and Barrett Resources entering into
the Merger Agreement and consummating the transactions contemplated thereby.

      Barrett Resources, directly or through subsidiaries, conducts business in
a number of states throughout the United States, some of which have enacted
takeover laws. Purchaser does not know whether any of these laws will, by their
terms, apply to the Offer or the Merger and has not attempted to comply with any
such laws. Should any person seek to apply any state takeover law, Purchaser
will take such action as then appears desirable, which may include challenging
the validity or applicability of any such statute in appropriate court
proceedings. In the event it is asserted that one or more state takeover laws is
applicable to the Offer or the Merger, and an appropriate court does not
determine that it is inapplicable or invalid as applied to the Offer, Purchaser
might be required to file certain information with, or receive approvals from,
the relevant state authorities. In addition, if enjoined, Purchaser might be
unable to accept for payment any Shares tendered pursuant to the Offer, or be
delayed in continuing or consummating the Offer and the Merger. In such case,
Purchaser may not be obligated to accept for payment any Shares tendered. See
Section 14, "Conditions of the Offer."

      BARRETT RESOURCES BYLAWS.  Article IV of the Barrett Resources Bylaws
restricts certain business combinations involving Interested Persons (as defined
in the Barrett Resources Bylaws). On May 7, 2001, the Barrett Resources Board
waived such restrictions by Independent Director Approval (as defined in the
Barrett Resources Bylaws), such that the restrictions do not and will not apply
with respect to or as a result of the Merger Agreement or the transactions
contemplated thereby, including the Offer and the Merger.

      ANTITRUST.  Under the HSR Act and the rules that have been promulgated
thereunder by the Federal Trade Commission (the "FTC"), certain acquisition
transactions may not be consummated unless certain information has been
furnished to the Antitrust Division of the Department of Justice (the "Antitrust
Division") and the FTC and certain waiting period requirements have been
satisfied. The acquisition of Shares by Purchaser pursuant to the Offer is
subject to such requirements.

      Barrett Resources and Williams expect to file Premerger Notification and
Report Forms in connection with the purchase of Shares pursuant to the Offer
with the Antitrust Division and the FTC on or about May 16, 2001. Under the
provisions of the HSR Act applicable to the Offer, the purchase of Shares
pursuant to the Offer may not be consummated until the expiration of a
15-calendar day waiting period following the filing by Williams. Accordingly, if
the forms are filed on May 16, 2001, the waiting period under the HSR Act
applicable to the purchase of Shares pursuant to the Offer will expire at 11:59
p.m., eastern time, on May 31, 2001, unless such waiting period is earlier
terminated by the FTC and the Antitrust Division or extended by a request from
the FTC or the Antitrust Division for additional information or documentary
material prior to the expiration of the waiting period. If the acquisition of
Shares is delayed pursuant to a request by the FTC or the Antitrust Division for
additional information or documentary material pursuant to the HSR Act, the
purchase of and payment for Shares will be deferred until 10 days after the
request is substantially complied with, unless the extended period expires on or
before the date when the initial 15-day period would otherwise have expired, or
unless the waiting period is sooner terminated by the FTC and the Antitrust
Division. Only one extension of such waiting period pursuant to a request for
additional information is authorized by the HSR Act and the rules promulgated
thereunder, except by court order. Any such extension of the waiting period will
not give rise to any withdrawal rights not otherwise provided for by applicable
law. See Section 4, "Withdrawal Rights". It is a condition to the Offer that the
waiting period applicable under the HSR Act to the Offer expire or be
terminated. See Section 14, "Conditions of the Offer". So long as the Merger
Agreement is in effect and any applicable waiting period under the HSR Act has
not expired or been terminated, Purchaser is obligated to extend the Offer from
time to time for a period or successive periods.

                                        46
   56

      The FTC and the Antitrust Division frequently scrutinize the legality
under the antitrust laws of transactions such as the proposed acquisition of
Shares by Purchaser pursuant to the Offer and the Merger. At any time before or
after the purchase of Shares pursuant to the Offer by Purchaser, the FTC or the
Antitrust Division could take such action under the antitrust laws as they deem
necessary or desirable in the public interest, including seeking to enjoin the
purchase of Shares pursuant to the Offer or seeking the divestiture of Shares
purchased by Purchaser or the divestiture of substantial assets of Williams,
Barrett Resources or their respective subsidiaries. Private parties and state
attorneys general may also bring legal action under federal or state antitrust
laws under certain circumstances. Based upon an examination of information
available to Williams relating to the businesses in which Williams, Barrett
Resources and their respective subsidiaries are engaged, Williams and Purchaser
believe that the Offer will not violate the applicable antitrust laws.
Nevertheless, there can be no assurance that a challenge to the Offer on
antitrust or competition grounds will not be made or, if such a challenge is
made, what the final result would be. See Section 14, "Conditions of the Offer".

      In addition, the antitrust and competition laws of certain foreign
jurisdictions require (or, in some instances, provide for on a voluntary basis)
notification of the transaction and the observance of pre-consummation waiting
periods. Barrett Resources and Williams will make any such required filings, if
any (and, if deemed in Barrett Resources' and Williams' interests, any such
voluntary filings), with the appropriate antitrust and competition authorities
contemporaneously with their filings under the HSR Act or shortly thereafter.
Based upon an examination of information available to Williams relating to the
businesses in which Williams, Barrett Resources and their respective
subsidiaries are engaged, Williams and Purchaser believe that the Offer will not
violate any such foreign antitrust and competition laws. Nevertheless, there can
be no assurance that a challenge to the Offer will not be made on antitrust or
competition grounds or, if such a challenge were made, what the final result
would be.

16. FEES AND EXPENSES.

      Williams and Purchaser retained Merrill Lynch to act as Dealer Manager in
connection with the Offer, for which Merrill Lynch will be paid $250,000 upon
execution of the agreement with respect to Merrill Lynch's engagement as Dealer
Manager, and an additional $250,000 upon completion of the Offer in addition to
reimbursement for reasonable out-of-pocket expenses. Williams has also retained
Merrill Lynch to render financial advisory services to Williams and Purchaser
concerning the acquisition of Barrett Resources, including rendering a fairness
opinion to the Board of Directors of Williams, for which Merrill Lynch will
receive customary compensation. Williams has also agreed to indemnify Merrill
Lynch against certain liabilities and expenses in connection with its
engagement, including liabilities under the federal securities laws.

      Merrill Lynch has provided financial advisory and financing services to
Williams and its affiliates in the past and may continue to render such
services, for which they have received and may continue to receive customary
compensation from Williams and its affiliates. In the ordinary course of
business, Merrill Lynch and its affiliates are engaged in securities trading and
brokerage activities as well as investment banking and financial advisory
services. In the ordinary course of their trading and brokerage activities,
Merrill Lynch and its affiliates may hold positions, for their own account and
for the accounts of customers, in equity, debt or other securities of Williams
or Barrett Resources.

      We have retained Georgeson Shareholder Communications, Inc. as Information
Agent in connection with the Offer. The Information Agent may contact holders of
Shares by mail, telephone, telex, telegraph and personal interview and may
request brokers, dealers and other nominee stockholders to forward material
relating to the Offer to beneficial owners of Shares. We will pay the
Information Agent reasonable and customary compensation for these services in
addition to reimbursing the Information Agent for its reasonable out-of-pocket
expenses. We have agreed to indemnify the Information Agent against certain
liabilities and expenses in connection with the Offer, including certain
liabilities under the federal securities laws.

      In addition, we have retained EquiServe as the Depositary. We will pay the
Depositary reasonable and customary compensation for its services in connection
with the Offer, will reimburse the Depositary

                                        47
   57

for its reasonable out-of-pocket expenses and will indemnify the Depositary
against certain liabilities and expenses, including certain liabilities under
the federal securities laws.

      Except as set forth above, we will not pay any fees or commissions to any
broker, dealer or other person for soliciting tenders of Shares pursuant to the
Offer. We will reimburse brokers, dealers, commercial banks and trust companies
and other nominees, upon request, for customary clerical and mailing expenses
incurred by them in forwarding offering materials to their customers.

17. MISCELLANEOUS.

      We are not aware of any jurisdiction where the making of the Offer is
prohibited by any administrative or judicial action pursuant to any valid state
statute. If we become aware of any valid state statute prohibiting the making of
the Offer or the acceptance of the Shares, we will make a good faith effort to
comply with that state statute. If, after a good faith effort, we cannot comply
with the state statute, we will not make the Offer to, nor will we accept
tenders from or on behalf of, the holders of Shares in that state. In any
jurisdiction where the securities, blue sky or other laws require the Offer to
be made by a licensed broker or dealer, the Offer shall be deemed to be made on
behalf of Purchaser by the Dealer Manager or one or more registered brokers or
dealers licensed under the laws of such jurisdiction.

      We have filed with the SEC a Tender Offer Statement on Schedule TO,
together with exhibits, furnishing certain additional information with respect
to the Offer, and may file amendments to our Schedule TO. Our Schedule TO and
any exhibits or amendments may be examined and copies may be obtained from the
SEC in the same manner as described in Section 8 with respect to information
concerning Barrett Resources, except that copies will not be available at the
regional offices of the SEC.

WE HAVE NOT AUTHORIZED ANY PERSON TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATION ON OUR BEHALF NOT CONTAINED IN THIS OFFER TO PURCHASE OR IN THE
LETTER OF TRANSMITTAL AND, IF GIVEN OR MADE, YOU SHOULD NOT RELY ON ANY SUCH
INFORMATION OR REPRESENTATION AS HAVING BEEN AUTHORIZED.

      Neither the delivery of the Offer to Purchase nor any purchase pursuant to
the Offer will under any circumstances create any implication that there has
been no change in the affairs of Williams, Purchaser, Barrett Resources or any
of their respective subsidiaries since the date as of which information is
furnished or the date of this Offer to Purchase.

                                          Resources Acquisition Corp.

May 14, 2001

                                        48
   58

                                   SCHEDULE I

           DIRECTORS AND EXECUTIVE OFFICERS OF WILLIAMS AND PURCHASER

      A.  DIRECTORS AND EXECUTIVE OFFICERS OF WILLIAMS.  The following table
sets forth the name and present principal occupation or employment, and material
occupations, positions, offices or employments for the past five years of each
director and executive officer of Williams. None of the directors and officers
of Williams listed below has, during the past five years, (i) been convicted in
a criminal proceeding or (ii) been a party to any judicial or administrative
proceeding that resulted in a judgment, decree or final order enjoining the
person from future violations of, or prohibiting activities subject to, federal
or state securities laws, or a finding of any violation of federal or state
securities laws. Unless otherwise indicated below, each occupation set forth
opposite each person refers to employment with Williams. The business address of
each such person is c/o The Williams Companies, One Williams Center, Tulsa, OK
74172, and each such person is a citizen of the United States of America.

1. DIRECTORS OF WILLIAMS

                                       DIRECTOR OF    CURRENT
                                        WILLIAMS       TERM     CURRENT POSITION AND PRINCIPAL OCCUPATION OR EMPLOYMENT;
NAME AND AGE                              SINCE       EXPIRES        MATERIAL POSITIONS HELD DURING LAST FIVE YEARS
- ------------                           -----------    -------   --------------------------------------------------------
                                                       
Hugh M. Chapman, 68..................     1999         2002     Director of Williams since 1999. Chairman of the Board
                                                                of Nations Bank South until 1997. Director of SCANA
                                                                Corporation, West Point Stevens and Print Pack, Inc.
Frank T. MacInnis, 54................     1998         2002     Director of Williams since 1998. Chairman and Chief
                                                                Executive Officer of EMCOR Group, Inc. since 1994.
                                                                Chairman of the Board of ComNet Communications, Inc. and
                                                                director of UTT Corporation.
Peter C. Meinig, 61..................     1993         2002     Director of Williams since 1993. Chairman and Chief
                                                                Executive Officer of HM International, Inc. Chairman of
                                                                Windsor Food Company, Ltd. and Ninth House, Inc.
Janice D. Stoney, 60.................     1999         2002     Director of Williams since 1999. Director of Whirpool
                                                                Corporation and Bridges Investment Fund.
Keith E. Bailey, 59..................     1998         2003     Director of Williams since 1988. Chairman of the Board
                                                                of Williams since 1994. President of Williams since
                                                                1992. Chief Executive Officer of Williams since 1994.
                                                                Chairman of the Board of Williams Communication Group,
                                                                Inc. until April 23, 2001. Director of Purchaser since
                                                                2001.
William E. Green, 64.................     1998         2003     Director of Williams since 1998. Founder of and Attorney
                                                                at William Green and Associates, a California law firm,
                                                                and Vice President, General Counsel and Secretary of
                                                                Information Network Radio Inc.

                                        49
   59

                                       DIRECTOR OF    CURRENT
                                        WILLIAMS       TERM     CURRENT POSITION AND PRINCIPAL OCCUPATION OR EMPLOYMENT;
NAME AND AGE                              SINCE       EXPIRES        MATERIAL POSITIONS HELD DURING LAST FIVE YEARS
- ------------                           -----------    -------   --------------------------------------------------------
                                                       
W.R. Howell, 65......................     1997         2003     Director of Williams since 1997. Chairman of the Board
                                                                and Chief Executive Officer of J.C. Penney until 1996.
                                                                Chairman Emeritus of J.C. Penney Company, Inc. Director
                                                                of Exxon Mobil Corporation, Warner-Lambert Company,
                                                                Bankers Trust, Halliburton Company and Central
                                                                Southwest.
James C. Lewis, 68...................     1978         2003     Director of Williams since 1978. Chairman of the Board
                                                                of Optimus Corporation. Director of CFT.
George A. Lorch, 59..................     2001         2003     Director of Williams since 2001. Chairman Emeritus of
                                                                Armstrong Holdings, Inc. Chairman of the Board and Chief
                                                                Executive Officer of Armstrong World Industries, Inc.
                                                                until 2000. Board member of Pfizer, Household
                                                                International and R.R. Donnelly.
Glenn A. Cox, 71.....................     1992         2004     Director of Williams since 1992. Director of Helmerich
                                                                and Payne, Inc.
Thomas H. Cruikshank, 69.............     1990         2004     Director of Williams since 1990. Chairman of and Chief
                                                                Executive Officer of Halliburton Company until 1996.
                                                                Director of Goodyear Tire & Rubber Company and Lehman
                                                                Bros. Holding, Inc.
Charles M. Lillis, 59................     2000         2004     Director of Williams since 2000. Co-founder and
                                                                principal of LoneTree Partners. Chairman of the Board
                                                                and Chief Executive Officer of MediaOne Group from 1995
                                                                until 2000. Director of SUPERVALU Inc. and Agilera, Inc.
Gordon R. Parker, 65.................     1987         2004     Director of Williams since 1987. Director of
                                                                Caterpillar, Inc. and Phelps Dodge Corporation.
Joseph H. Williams, 67...............     1969         2004     Director of Williams since 1969. Director of The
                                                                Prudential Insurance Co. of America.

                                        50
   60

2. EXECUTIVE OFFICERS OF WILLIAMS

Except as set forth below, all of the officers of Williams have been employed by
Williams or its subsidiaries as officers or otherwise for more than five years
and have had no other employment during the period.

                                       OFFICER OF
                                        WILLIAMS     CURRENT POSITION AND PRINCIPAL OCCUPATION OR EMPLOYMENT;
NAME AND AGE                             SINCE            MATERIAL POSITIONS HELD DURING LAST FIVE YEARS
- ------------                           ----------    --------------------------------------------------------
                                               
Keith E. Bailey, 59..................     1994       Director of Williams since 1988. Chairman of the Board
                                                     of Williams since 1994. President of Williams since
                                                     1992. Chief Executive Officer of Williams since 1994.
                                                     Chairman of the Board of Williams Communications Group,
                                                     Inc. until April 23, 2001. Director of Purchaser since
                                                     2001.
Michael P. Johnson, Sr., 53..........     2000       Executive Officer of Williams since 2000. Senior Vice
                                                     President of Human Resources of Williams. Director of
                                                     Williams Communications Group, Inc. until April 23,
                                                     2001. Prior to 2000 and for more than five year prior to
                                                     joining Williams held various officer positions with
                                                     Amoco Corporation.
Jack D. McCarthy, 58.................     1992       Executive Officer of Williams since 1992. Senior Vice
                                                     President of Finance (Principal Financial Officer) of
                                                     Williams. Director of Williams Communications Group,
                                                     Inc. until April 23, 2001.
William G. von Glahn, 57.............     1996       Executive Officer of Williams since 1996. Senior Vice
                                                     President and General Counsel of Williams.
Gary R. Belitz, 51...................     1992       Executive Officer of Williams since 1992. Controller
                                                     (Principal Accounting Officer) of Williams.
Steven J. Malcolm, 52................     1998       Executive Officer of Williams since 1998. Executive Vice
                                                     President of Williams since March 2001. President and
                                                     Chief Executive Officer of Williams Energy Services, LLC
                                                     since 1998. Director of Williams Communications Group,
                                                     Inc. until April 23, 2001. Director of Purchaser since
                                                     2001.
Cuba Wadlington, Jr., 57.............     2000       Executive Officer of Williams since 2000. President and
                                                     Chief Executive Officer of Williams Gas Pipeline Company
                                                     LLC since 2000. Director of Williams Communications
                                                     Group, Inc. until April 23, 2001.

      B.  DIRECTORS AND EXECUTIVE OFFICERS OF PURCHASER.  The following table
sets forth the name and present principal occupation or employment, and material
occupations, positions, offices or employments for the past five years of each
director and executive officer of Purchaser. None of the directors and officers
of Purchaser listed below has, during the past five years, (i) been convicted in
a criminal proceeding or (ii) been a party to any judicial or administrative
proceeding that resulted in a judgment, decree or final order enjoining the
person from future violations of, or prohibiting activities subject to, federal
or state securities laws, or a finding of any violation of federal or state
securities laws. Unless otherwise indicated below, each occupation set forth
opposite each person refers to employment with Williams. The business address of
each such person is c/o The Williams Companies, One Williams Center, Tulsa, OK
74172, and each such person is a citizen of the United States of America.

                                        51
   61

1. DIRECTORS OF PURCHASER

                                       DIRECTOR OF
                                        PURCHASER     CURRENT POSITION AND PRINCIPAL OCCUPATION OR EMPLOYMENT;
NAME AND AGE                              SINCE            MATERIAL POSITIONS HELD DURING LAST FIVE YEARS
- ------------                           -----------    --------------------------------------------------------
                                                
Keith E. Bailey, 59..................  May 2001       Director of Purchaser since 2001. Director of Williams
                                                      since 1988. Chairman of the Board of Williams since
                                                      1994. President of Williams since 1992. Chief Executive
                                                      Officer of Williams since 1994. Chairman of the Board of
                                                      Williams Communications Group, Inc. until April 23,
                                                      2001.
Stephen J. Malcolm, 52...............  May 2001       Director of Purchaser since 2001. Executive Vice
                                                      President of Williams since March 2001. Executive
                                                      Officer of Williams since 1998. President and Chief
                                                      Executive Officer of Williams Energy Services, LLC since
                                                      1998. Director of Williams Communications Group, Inc.
                                                      until April 23, 2001.
Ralph A. Hill, 41....................  May 2001       Director of Purchaser since 2001. Senior Vice President
                                                      of Williams Energy Services, LLC since 1998. General
                                                      Manager of Exploration and Production of Williams Energy
                                                      Services, LLC since 1996.

2. EXECUTIVE OFFICERS OF PURCHASER

                                       DIRECTOR OF
                                        PURCHASER     CURRENT POSITION AND PRINCIPAL OCCUPATION OR EMPLOYMENT;
NAME AND AGE                              SINCE            MATERIAL POSITIONS HELD DURING LAST FIVE YEARS
- ------------                           -----------    --------------------------------------------------------
                                                
Steven J. Malcolm, 52................  May 2001       President of Purchaser since 2001. Executive Vice
                                                      President of Williams since March 2001. Executive
                                                      Officer of Williams since 1998. President and Chief
                                                      Executive Officer of Williams Energy Services, LLC since
                                                      1998. Director of Purchaser since 2001. Director of
                                                      Williams Communications Group, Inc. until April 23,
                                                      2001.
James G. Ivey, 49....................  May 2001       Treasurer of Purchaser since 2001. Treasurer of Williams
                                                      since 1995.
Ralph A. Hill, 41....................  May 2001       Senior Vice President of Purchaser since 2001. Director
                                                      of Purchaser since 2001. Senior Vice President of
                                                      Williams Energy Services, LLC since 1998. General
                                                      Manager of Exploration and Production of Williams Energy
                                                      Services, LLC since 1996.
Bryan K. Guderian, 41................  May 2001       Vice President of Purchaser since 2001. Vice President
                                                      of Williams Production Company, LLC since 1998. Director
                                                      of Land & Gas Management, Williams Production Company,
                                                      1996-1998.

                                        52
   62

      Facsimile copies of Letters of Transmittal, properly completed and duly
executed, will be accepted. The appropriate Letter of Transmittal, certificates
for Shares and any other required documents should be sent or delivered by each
stockholder of Barrett Resources or his broker, dealer, commercial bank, trust
company or other nominee to the Depositary at one of its addresses set forth
below:

                        The Depositary for the Offer is:

                         EQUISERVE TRUST COMPANY, N.A.

                                                          
           By Mail:                  By Overnight Courier:                 By Hand:
    Attn: Corporate Actions         Attn: Corporate Actions         Attn: Corporate Actions
        P.O. Box 43025                40 Campanelli Drive       Securities Transfer & Reporting
   Providence, RI 02940-3025          Braintree, MA 02184               Services, Inc.
                                                                         c/o EquiServe
                                                                 100 William Street, Galleria
                                                                      New York, NY 10038

                                 By Facsimile:
                        (for Eligible Institutions only)

                                 (781) 575-4826

                        Confirm Facsimile By Telephone:

                                 (781) 575-4816

      You may direct questions and requests for assistance to the Information
Agent or the Dealer Manager at their respective telephone numbers and addresses
set forth below. You may obtain additional copies of this Offer to Purchase, the
Letter of Transmittal, the Notice of Guaranteed Delivery and other tender offer
materials from the Information Agent as set forth below and they will be
furnished promptly at our expense. You may also contact your broker, dealer,
commercial bank, trust company or other nominee for assistance concerning the
Offer.

                    The Information Agent for the Offer is:

                          [Georgeson Shareholder logo]

                          17 State Street, 10th Floor
                            New York, New York 10004
                 Banks and Brokers Call Collect: (212) 440-9800
                   All Others Call Toll Free: (800) 223-2064

                      The Dealer Manager for the Offer is:

                              MERRILL LYNCH & CO.

                          Four World Financial Center
                            New York, New York 10080
                          Call Collect: (212) 236-3790
   1
                                                                 Exhibit (a)(2)

                             LETTER OF TRANSMITTAL

                        TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

              PURSUANT TO THE OFFER TO PURCHASE DATED MAY 14, 2001

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       TO

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.
- --------------------------------------------------------------------------------
     THE OFFER, PRORATION PERIOD AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00
MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11, 2001, UNLESS THE OFFER IS EXTENDED.
- --------------------------------------------------------------------------------

                        The Depositary for the Offer is:

                         EQUISERVE TRUST COMPANY, N.A.

                                                                
            By Mail:                     By Overnight Courier:                    By Hand:
     Attn: Corporate Actions            Attn: Corporate Actions            Attn: Corporate Actions
         P.O. Box 43025                   40 Campanelli Drive               Securities Transfer &
    Providence, RI 02940-3025             Braintree, MA 02184             Reporting Services, Inc.
                                                                                C/O EquiServe
                                                                        100 William Street, Galleria
                                                                             New York, NY 10038

                                             By Facsimile:
                                   (for Eligible Institutions only)
                                            (781) 575-4826
                                    Confirm Facsimile By Telephone:
                                            (781) 575-4816

- ------------------------------------------------------------------------------------------------------------------------------
                                                DESCRIPTION OF SHARES TENDERED
- ------------------------------------------------------------------------------------------------------------------------------
               NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)                          SHARE CERTIFICATE(S) ENCLOSED
(PLEASE FILL IN, IF BLANK EXACTLY AS NAME(S) APPEAR(S) ON SHARE CERTIFICATE(S)  (ATTACH ADDITIONAL SIGNED LIST IF NECESSARY)
- ------------------------------------------------------------------------------------------------------------------------------
                                                                                                 
                                                                                        SHARE             NUMBER OF SHARES
                                                                               CERTIFICATE NUMBER(S)*        TENDERED**
                                                                               ----------------------------------------------

                                                                               ----------------------------------------------

                                                                               ----------------------------------------------

                                                                               ----------------------------------------------

                                                                               ----------------------------------------------

                                                                               ----------------------------------------------

                                                                               ----------------------------------------------
                                                                                    TOTAL SHARES
- ------------------------------------------------------------------------------------------------------------------------------

 * Certificate numbers are not required if tender is made by book-entry
   transfer.

** If you desire to tender fewer than all Shares represented by a certificate
   listed above, please indicate in this column the number of Shares you wish to
   tender. Otherwise, all Shares represented by such certificate will be deemed
   to have been tendered. See Instruction 4.
   2

                               LOST CERTIFICATES

[ ]  I have lost my Certificates that represented ________ Shares and require
     assistance in obtaining replacement Certificates. I understand that I must
     contact the EquiServe, the Transfer Agent for Barrett Resources, to obtain
     instructions for replacing lost Certificates. Call EquiServe at
     1-800-736-3001. (See Instruction 9.)

      DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE, OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE TO A NUMBER OTHER
THAN AS LISTED ABOVE DOES NOT CONSTITUTE A VALID DELIVERY. YOU MUST SIGN THIS
LETTER OF TRANSMITTAL WHERE INDICATED BELOW.

      THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

      This Letter of Transmittal is to be completed by stockholders of Barrett
Resources Corporation if certificates ("Share Certificates") representing shares
of common stock, par value $0.01 per share, (including the associated Rights (as
defined herein), the "Shares"), are to be forwarded herewith or, unless an
Agent's Message (as defined in the Offer to Purchase) is utilized, if delivery
of Shares is to be made by book-entry transfer to an account maintained by
EquiServe Trust Company, N.A. ("EquiServe" or the "Depositary") at The
Depositary Trust Company (the "Book-Entry Transfer Facility") pursuant to the
procedures set forth in Section 3 of the Offer to Purchase dated May 14, 2001
(the "Offer to Purchase"). DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER
FACILITY IN ACCORDANCE WITH THE BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES
NOT CONSTITUTE DELIVERY TO THE DEPOSITARY.

      Stockholders whose Share Certificates are not immediately available or who
cannot deliver their Share Certificates and all other required documents to the
Depositary on or prior to the expiration date of the Offer or who are unable to
complete the procedure for book-entry transfer prior to the expiration date of
the Offer may nevertheless tender their Shares pursuant to the guaranteed
delivery procedures set forth in Section 3 of the Offer to Purchase. See
Instruction 2 below.

NOTE:  SIGNATURE(S) MUST BE PROVIDED BELOW. PLEASE READ THE INSTRUCTIONS SET
       FORTH IN THIS LETTER OF TRANSMITTAL CAREFULLY.

[ ]  CHECK HERE IF SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE TO AN
     ACCOUNT MAINTAINED BY THE DEPOSITARY WITH THE BOOK-ENTRY TRANSFER FACILITY
     AND COMPLETE THE FOLLOWING:
     Name of Tendering Institution:
    ----------------------------------------------------------------------------

     Provide Account Number and Transaction Code Number:

     Account Number:
    ----------------------------------------------------------------------------
     Transaction Code Number:
    ----------------------------------------------------------------------------

[ ] CHECK HERE IF CERTIFICATES FOR TENDERED SHARES ARE BEING DELIVERED PURSUANT
    TO A NOTICE OF GUARANTEED DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND
    COMPLETE THE FOLLOWING. PLEASE ENCLOSE A PHOTOCOPY OF SUCH NOTICE OF
    GUARANTEED DELIVERY.
    Name(s) of Registered Holder(s):
    ----------------------------------------------------------------------------
    Window Ticket Number (if any):
    ----------------------------------------------------------------------------
    Date of Execution of Notice of Guaranteed Delivery:
    --------------------------------------------------------------
    Name of Institution which Guaranteed Delivery:
    -------------------------------------------------------------------

IF DELIVERED BY BOOK-ENTRY TRANSFER TO THE BOOK-ENTRY TRANSFER FACILITY, CHECK
BOX:  [ ]

Account Number:
- --------------------------------------------------------------------------------

Transaction Code Number:
- --------------------------------------------------------------------------------

                                        2
   3

Ladies and Gentlemen:

      The undersigned hereby tenders to Resources Acquisition Corp.,
("Purchaser"), a Delaware corporation and a wholly-owned subsidiary of The
Williams Companies, Inc. ("Williams"), the above-described shares of common
stock, par value $0.01 per share (including the associated Rights (as defined
below), the "Shares"), of Barrett Resources Corporation, a Delaware corporation
("Barrett Resources"), pursuant to Purchaser's offer to purchase 16,730,502
Shares at $73.00 per Share, net to the seller in cash, without interest, upon
the terms and subject to the conditions set forth in the Offer to Purchase dated
May 14, 2001 (the "Offer to Purchase"), receipt of which is hereby acknowledged,
and in this Letter of Transmittal (which, as amended or supplemented from time
to time, together with the Offer to Purchase constitute the "Offer"). As used
herein, "Rights" means the preferred stock purchase rights associated with the
Shares and outstanding under the Rights Agreement (the "Rights Agreement") dated
as of August 5, 1997 by and between Barrett Resources and Fleet National Bank,
as successor to BankBoston, N.A., as Rights Agent, as amended. Unless the
context otherwise requires, all references to Shares shall be deemed to include
the associated Rights, and all references to the Rights shall be deemed to
include the benefits that may inure to holders of the Rights pursuant to the
Rights Agreement.

      Subject to, and effective upon, acceptance for payment of the Shares
tendered herewith, in accordance with the terms of the Offer, the undersigned
hereby sells, assigns and transfers to or upon the order of Purchaser all right,
title and interest in and to all the Shares that are being tendered hereby and
all dividends, non-cash distributions (including, without limitation,
distributions of additional Shares) and any rights declared, paid or distributed
in respect of such Shares on or after May 7, 2001 (collectively,
"Distributions") and irrevocably appoints EquiServe Trust Company, N.A. (the
"Depositary"), as the true and lawful agent and attorney-in-fact of the
undersigned with respect to such Shares and all Distributions, with full power
of substitution (such power of attorney being deemed to be an irrevocable power
coupled with an interest), to (i) deliver certificates representing Shares
("Share Certificates") and all Distributions, or transfer ownership of such
Shares and all Distributions on the account books maintained by the Book-Entry
Transfer Facility, together, in either case, with all accompanying evidences of
transfer and authenticity, to or upon the order of Purchaser; (ii) present such
Shares and all Distributions for transfer on the books of Barrett Resources; and
(iii) receive all benefits and otherwise exercise all rights of beneficial
ownership of such Shares and all Distributions, all in accordance with the terms
of the Offer.

      Barrett Resources has distributed one Right for each outstanding Share
pursuant to the Rights Agreement. The Rights are currently evidenced by and
trade with certificates evidencing the Shares. Barrett Resources has taken such
action so as to make the Rights Agreement inapplicable to Williams, Purchaser
and their respective affiliates and associates in connection with the
transactions contemplated by the Merger Agreement (as defined in the Offer to
Purchase).

      The undersigned hereby irrevocably appoints each of William G. von Glahn
and Jack D. McCarthy as agent, attorney-in-fact and proxy of the undersigned,
each with full power of substitution and resubstitution, to vote in such manner
as such attorney and proxy or his substitute shall, in his sole discretion, deem
proper and otherwise act (by written consent or otherwise) with respect to all
the Shares tendered hereby which have been accepted for payment by Purchaser
prior to the time of such vote or other action and all Shares and other
securities issued in Distributions in respect of such Shares, which the
undersigned is entitled to vote at any meeting of stockholders of Barrett
Resources (whether annual or special and whether or not an adjourned or
postponed meeting) or consent in lieu of any such meeting or otherwise. This
proxy and power of attorney is coupled with an interest in the Shares tendered
hereby, is irrevocable and is granted in consideration of, and is effective
upon, the acceptance for payment of such Shares by Purchaser in accordance with
the terms of the Offer. Such acceptance for payment shall revoke all other
proxies and powers of attorney granted by the undersigned at any time with
respect to such Shares (and all Shares and other securities issued in
Distributions in respect of such Shares), and no subsequent proxy or power of
attorney shall be given or written consent executed (and if given or executed,
shall not be effective) by the undersigned with respect thereto. The undersigned
understands that, in order for Shares to be deemed validly tendered, immediately
upon Purchaser's acceptance of such Shares for payment, Purchaser or its
designee must be able to exercise full voting, consent and other rights with
respect to such Shares and Distributions, including, without limitation, voting
at any meeting of Barrett Resources' stockholders.

                                        3
   4

      The undersigned hereby represents and warrants that the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby and all Distributions, and that when such Shares are accepted
for payment by Purchaser, Purchaser will acquire good, marketable and
unencumbered title thereto and to all Distributions, free and clear of all
liens, restrictions, charges and encumbrances, and that none of such Shares or
Distributions will be subject to any adverse claim. The undersigned, upon
request, shall execute and deliver all additional documents deemed by the
Depositary or Purchaser to be necessary or desirable to complete the sale,
assignment and transfer of the Shares tendered hereby and all Distributions. In
addition, the undersigned shall remit and transfer promptly to the Depositary
for the account of Purchaser all Distributions in respect of the Shares tendered
hereby, accompanied by appropriate documentation of transfer, and pending such
remittance and transfer or appropriate assurance thereof, Purchaser shall be
entitled to all rights and privileges as owner of each such Distribution and may
withhold the entire purchase price of the Shares tendered hereby, or deduct from
such purchase price, the amount or value of such Distribution as determined by
Purchaser in its sole discretion.

      No authority herein conferred or agreed to be conferred shall be affected
by, and all such authority shall survive, the death or incapacity of the
undersigned. All obligations of the undersigned hereunder shall be binding upon
the heirs, personal representatives, successors and assigns of the undersigned.
Except as stated in the Offer to Purchase, this tender is irrevocable. See
Section 4 in the Offer to Purchase.

      The undersigned understands that tenders of Shares pursuant to any one of
the procedures described in Section 3 of the Offer to Purchase and in the
instructions hereto will constitute the undersigned's acceptance of the terms
and conditions of the Offer. Purchaser's acceptance of such Shares for payment
will constitute a binding agreement between the undersigned and Purchaser upon
the terms and subject to the conditions of the Offer, as well as the
undersigned's representation and warranty to Purchaser and Barrett Resources
that (i) the undersigned has a net long position in the Shares or equivalent
securities being tendered within the meaning of Rule 14e-4 promulgated under the
Securities Exchange Act of 1934, as amended (the "Exchange Act") and (ii) the
tender of such Shares complies with Rule 14e-4 of the Exchange Act. Without
limiting the foregoing, if the price to be paid in the Offer is amended in
accordance with the Offer, the price to be paid to the undersigned will be the
amended price notwithstanding the fact that a different price is stated in this
Letter of Transmittal. The undersigned recognizes that under certain
circumstances set forth in the Offer to Purchase, Purchaser may not be required
to accept for payment any of the Shares tendered hereby.

      Unless otherwise indicated herein in the box entitled "Special Payment
Instructions," please issue the check for the purchase price of all Shares
purchased, and return all Share Certificates not purchased or not tendered in
the name(s) of the registered holder(s) appearing above in the box entitled
"Description of Shares Tendered." Similarly, unless otherwise indicated in the
box entitled "Special Delivery Instructions," please mail the check for the
purchase price of all Shares purchased and all Share Certificates not tendered
or not purchased (and accompanying documents, as appropriate) to the address(es)
of the registered holder(s) appearing above in the box entitled "Description of
Shares Tendered." In the event that the boxes entitled "Special Payment
Instructions" and "Special Delivery Instruction" are both completed, please
issue the check for the purchase price of all Shares purchased and return all
Share Certificates not purchased or not tendered in the name(s) of, and mail
such check and Share Certificates to, the person(s) so indicated. Unless
otherwise indicated herein in the box entitled "Special Payment Instructions,"
please credit any Shares tendered hereby and delivered by book-entry transfer,
but which are not purchased, by crediting the account at the Book-Entry Transfer
Facility. The undersigned recognizes that Purchaser has no obligation, pursuant
to the Special Payment Instructions, to transfer any Shares from the name of the
registered holder(s) thereof if Purchaser does not purchase any of the Shares
tendered hereby.

      The undersigned understands that Purchaser reserves the right to transfer
or assign, in whole at any time, or in part from time to time, to one or more of
its affiliates, the right to purchase all or any portion of the Shares tendered
pursuant to the Offer, but any such transfer or assignment will not relieve
Purchaser of its obligations under the Offer and will in no way prejudice the
rights of tendering stockholders to receive payment for Shares validly tendered
and accepted for payment pursuant to the Offer.

      The undersigned understands that Purchaser is offering to purchase
16,730,502 shares, and that in the event that more than 16,730,502 Shares are
validly tendered and not withdrawn as of the Expiration Date (as defined in the
Offer to Purchase) and proration of tendered Shares is required, because of the
difficulty of determining the precise

                                        4
   5

number of Shares properly tendered and not withdrawn (due in part to the
guaranteed delivery procedure described under Section 3 of the Offer to
Purchase), the Purchaser does not expect that it will be able to announce the
final results of such proration or pay for any Shares until at least five New
York Stock Exchange trading days after the Expiration Date. Preliminary results
of proration will be announced by press release as promptly as practicable after
the Expiration Date. Stockholders may obtain such preliminary information from
the Information Agent and may be able to obtain such information from their
brokers. Tendering stockholders will not receive payment for Shares accepted for
payment pursuant to the Offer until the final proration factor is known.

                          SPECIAL PAYMENT INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

     To be completed ONLY if Share Certificates not tendered or purchased and/or
the check for the purchase price of the Shares purchased are to be issued in the
name of and sent to someone other than the undersigned, or if Shares tendered by
book-entry transfer which are not purchased are to be returned by credit to an
account maintained at the Book-Entry Transfer Facility other than the account
indicated above.

Issue:

       [ ] Check

           and/or

       [ ] Share Certificates

Name:
- -----------------------------------------------
                                    (PLEASE PRINT)

Address:
- ---------------------------------------------

- ------------------------------------------------------
                               (INCLUDE ZIP CODE)

- ------------------------------------------------------
              (TAXPAYER IDENTIFICATION NO. OR SOCIAL SECURITY NO.)
                   (ALSO COMPLETE SUBSTITUTE FORM W-9 BELOW)

[ ] Credit unpurchased Shares tendered by book-entry transfer to the Book-Entry
    Transfer Facility account set forth below:

- ------------------------------------------------------
                                (ACCOUNT NUMBER)

                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

     To be completed ONLY if Share Certificates not tendered or not purchased
and/or the check for the purchase price of the Shares purchased are to be sent
to someone other than the undersigned, or to the undersigned at an address other
than that shown above.

Mail:

       [ ] Check

           and/or

       [ ] Share Certificates

Name:
- -----------------------------------------------
                                    (PLEASE PRINT)

Address:
- ---------------------------------------------

- ------------------------------------------------------
                               (INCLUDE ZIP CODE)

- ------------------------------------------------------
             (TAXPAYER IDENTIFICATION CODE OR SOCIAL SECURITY NO.)

                                        5
   6

                                   SIGN HERE
                   (AND PLEASE COMPLETE SUBSTITUTE FORM W-9)

- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                          (SIGNATURE(S) OF HOLDER(S))

Dated:
- --------------------------- , 2001

(Must be signed by registered holder(s) exactly as name(s) appear(s) on Share
Certificate(s) and/or certificates representing Rights, if any, or on a security
position listing or by person(s) authorized to become registered holder(s) by
Share Certificates and documents transmitted herewith. If a signature is by an
officer on behalf of a corporation or by an executor, administrator, trustee,
guardian, attorney-in-fact, agent or other person acting in a fiduciary or
representative capacity, please provide the following information. See
Instructions 1 and 5.)

Name(s):------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                                 (PLEASE PRINT)

Name of Firm:
- --------------------------------------------------------------------------------

Capacity (full title):
- --------------------------------------------------------------------------------

Address:
- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                               (INCLUDE ZIP CODE)

(Area Code) Telephone Number:
- --------------------------------------------------------------------------------

Taxpayer Identification or Social Security No.:
           ---------------------------------------------------------------------
                           (SEE SUBSTITUTE FORM W-9)

                           GUARANTEE OF SIGNATURE(S)
                   (IF REQUIRED -- SEE INSTRUCTIONS 1 AND 5)

Authorized Signature:
- --------------------------------------------------------------------------------

Name:
- --------------------------------------------------------------------------------
                                 (PLEASE PRINT)

Name of Firm:
- --------------------------------------------------------------------------------

Address:
- --------------------------------------------------------------------------------

Zip Code:
- ------------------------------

(Area Code) Telephone No.:
- --------------------------------------------------------------------------------

Dated:
- --------------------------- , 2001

                                        6
   7

                                  INSTRUCTIONS

             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER

      To complete the Letter of Transmittal, you must do the following:

      - Fill in the box entitled "Description of Shares Being Tendered."

      - Sign and date the Letter of Transmittal in the box entitled "Sign Here."

      - Fill in and sign in the box entitled "Substitute Form W-9" (or, if you
        are a foreign stockholder, request and complete an appropriate Form W-8
        in lieu of Substitute Form W-9)."

      In completing the Letter of Transmittal, you may (but are not required to)
also do the following:

      - If you want the payment for any Shares purchased issued in the name of
        another person, complete the box entitled "Special Payment
        Instructions."

      - If you want any certificate for Shares not tendered or Shares not
        purchased, including as a result of proration, issued in the name of
        another person, complete the box entitled "Special Payment
        Instructions."

      - If you want any payment for Shares or certificate for Shares not
        tendered or purchased, including as a result of proration, delivered to
        an address other than that appearing under your signature, complete the
        box entitled "Special Delivery Instructions."

      - If you complete the box entitled "Special Payment Instructions" or
        "Special Delivery Instructions," you must have your signature guaranteed
        by an Eligible Institution (as defined in Instruction 1 below) unless
        the Letter of Transmittal is signed by an Eligible Institution.

      1.  GUARANTEE OF SIGNATURES.  All signatures on this Letter of Transmittal
must be guaranteed by a bank, broker, dealer, credit union, savings association
or other entity that is a member in good standing of the Securities Transfer
Agents Medallion Program (an "Eligible Institution"), unless (i) this Letter of
Transmittal is signed by the registered holder(s) (which term, for purposes of
this document, shall include any participant in the Book-Entry Transfer Facility
whose name appears on a security position listing as the owner of Shares) of the
Shares tendered hereby and such holder(s) has not completed either the box
entitled "Special Payment Instructions" or the box entitled "Special Delivery
Instructions" herein or (ii) such Shares are tendered for the account of an
Eligible Institution. If a Share Certificate is registered in the name of a
person other than the person signing this Letter of Transmittal, or if payment
is to be made or a Share Certificate not accepted for payment and not tendered
is to be returned to a person other than the registered holder(s), then such
Share Certificate must be endorsed or accompanied by appropriate stock powers,
in either case signed exactly as the name(s) of the registered holder(s) appear
on such Share Certificate, with the signatures on such Share Certificate or
stock powers guaranteed as described above. See Instruction 5.

      2.  DELIVERY OF LETTER OF TRANSMITTAL AND SHARE CERTIFICATES.  This Letter
of Transmittal is to be used either if Share Certificates (or certificates
representing Rights ("Rights Certificates") if any) are to be forwarded herewith
or, unless an Agent's Message (as defined below) is used, if Shares are to be
delivered by book-entry transfer pursuant to the procedure set forth in Section
3 of the Offer to Purchase. Share Certificates representing all physically
tendered Shares, or confirmation of a book-entry transfer, if such procedure is
available, into the Depositary's account at the Book-Entry Transfer Facility
("Book-Entry Confirmation") of all Shares delivered by book-entry transfer
together with a properly completed and duly executed Letter of Transmittal (or
facsimile thereof), or an Agent's Message in the case of book-entry transfer,
and any other documents required by this Letter of Transmittal, must be received
by the Depositary at one of its addresses set forth herein prior to the
Expiration Date of the Offer. If Share Certificates are forwarded to the
Depositary in multiple deliveries, a properly completed and duly executed Letter
of Transmittal must accompany each such delivery.

      Stockholders whose Share Certificates (and/or Rights Certificates, if any)
are not immediately available, who cannot deliver their Share Certificates
and/or Rights Certificates and all other required documents to the Depositary
prior to the Expiration Date of the Offer or who cannot complete the procedure
for delivery by book-entry transfer on a timely basis may tender their Shares
pursuant to the guaranteed delivery procedure described in Section 3 of the

                                        7
   8

Offer to Purchase. Pursuant to such procedure: (i) such tender must be made by
or through an Eligible Institution; (ii) a properly completed and duly executed
Notice of Guaranteed Delivery, substantially in the form made available by
Purchaser, must be received by the Depositary prior to the Expiration Date of
the Offer; and (iii) the Share Certificates representing all physically
delivered Shares in proper form for transfer by delivery, or Book-Entry
Confirmation of all Shares and Rights delivered by book-entry transfer, in each
case together with a Letter of Transmittal (or facsimile thereof), properly
completed and duly executed, with any required signature guarantees (or, in the
case of a book-entry transfer, an Agent's Message), and any other documents
required by this Letter of Transmittal, must be received by the Depositary
within three New York Stock Exchange trading days after the date of execution of
such Notice of Guaranteed Delivery, all as described in Section 3 of the Offer
to Purchase.

      The term "Agent's Message" means a message, transmitted by the Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of the
Book-Entry Confirmation, which states that the Book-Entry Transfer Facility has
received an express acknowledgment from the participants in the Book-Entry
Transfer Facility tendering the Shares that such participant has received this
Letter of Transmittal and agrees to be bound by the terms of this Letter of
Transmittal and that Purchaser may enforce such agreement against such
participant.

      THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, SHARE CERTIFICATES,
RIGHTS CERTIFICATES, IF ANY, AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING
DELIVERY THROUGH THE BOOK-ENTRY TRANSFER FACILITY, IS AT THE OPTION AND RISK OF
THE TENDERING STOCKHOLDER, AND THE DELIVERY WILL BE DEEMED MADE ONLY WHEN
ACTUALLY RECEIVED BY THE DEPOSITARY (INCLUDING, IN THE CASE OF A BOOK-ENTRY
TRANSFER, BY BOOK-ENTRY CONFIRMATION). IF DELIVERY IS BY MAIL, REGISTERED MAIL
WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES,
SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

      No alternative, conditional or contingent tenders will be accepted and no
fractional Shares will be purchased. By execution of this Letter of Transmittal
(or facsimile hereof), all tendering stockholders waive any right to receive any
notice of the acceptance of their Shares for payment.

      3.  INADEQUATE SPACE.  If the space provided herein under "Description of
Shares Tendered" is inadequate, the certificate numbers, the number of Shares
represented by such Share Certificates and the number of Shares tendered should
be listed on a separate signed schedule and attached hereto.

      4.  PARTIAL TENDERS (NOT APPLICABLE TO STOCKHOLDERS WHO TENDER BY
BOOK-ENTRY TRANSFER).  If fewer than all the Shares represented by any Share
Certificate delivered to the Depositary herewith are to be tendered hereby, fill
in the number of Shares which are to be tendered in the box entitled "Number of
Shares Tendered." In such cases, a new certificate representing the remainder of
the Shares that were represented by the Share Certificates delivered to the
Depositary herewith will be sent to each person signing this Letter of
Transmittal, unless otherwise provided in the box entitled "Special Delivery
Instructions" herein, as soon as practicable after the expiration or termination
of the Offer. All Shares represented by Share Certificates delivered to the
Depositary will be deemed to have been tendered unless otherwise indicated.

      5.  SIGNATURES ON LETTER OF TRANSMITTAL, STOCK POWERS AND ENDORSEMENTS.
If this Letter of Transmittal is signed by the registered holder(s) of the
Shares tendered hereby, the signature(s) must correspond with the name(s) as
written on the face of the Share Certificates evidencing such Shares without
alteration, enlargement or any other change whatsoever.

      If any Share tendered hereby is owned of record by two or more persons,
each such person must sign this Letter of Transmittal.

      If any of the Shares tendered hereby are registered in the names of
different holders, it will be necessary to complete, sign and submit as many
separate Letters of Transmittal as there are different registrations of such
Shares.

      If this Letter of Transmittal is signed by the registered holder(s) of the
Shares tendered hereby, no endorsements of Share Certificates or separate stock
powers are required, unless payment is to be made to, or Share Certificates not
tendered or not purchased are to be issued in the name of, a person other than
the registered holder(s), in which case, the Share Certificate(s) representing
the Shares tendered hereby must be endorsed or accompanied by appropriate stock
powers, in either case signed exactly as the name(s) of the registered holder(s)

                                        8
   9

appear on such Share Certificate(s). Signatures on such Share Certificate(s) and
stock powers must be guaranteed by an Eligible Institution.

      If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Shares tendered hereby, the Share Certificate(s)
representing the Shares tendered hereby must be endorsed or accompanied by
appropriate stock powers, in either case signed exactly as the name(s) of the
registered holder(s) appear(s) on such Share Certificate(s). Signatures on such
Share Certificate(s) and stock powers must be guaranteed by an Eligible
Institution.

      If this Letter of Transmittal or any certificate or stock power is signed
by a trustee, executor, administrator, guardian, attorney-in-fact, officer of a
corporation or other person acting in a fiduciary or representative capacity,
such person should so indicate when signing, and proper evidence satisfactory to
Purchaser of such person's authority to so act must be submitted.

      6.  STOCK TRANSFER TAXES.  Except as otherwise provided in this
Instruction 6, Barrett Resources will pay all stock transfer taxes with respect
to the sale and transfer of any Shares to Purchaser or Purchaser's order
pursuant to the Offer. If, however, payment of the purchase price of any Shares
purchased is to be made to, or Share Certificate(s) representing Shares not
tendered or not purchased are to be issued in the name of, a person other than
the registered holder(s), the amount of any stock transfer taxes (whether
imposed on the registered holder(s), such other person or otherwise) payable on
account of the transfer to such other person will be deducted from the purchase
price of such Shares purchased, unless evidence satisfactory to Barrett
Resources of the payment of such taxes, or exemption therefrom, is submitted.

      EXCEPT AS PROVIDED IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE SHARE CERTIFICATES REPRESENTING THE
SHARES TENDERED HEREBY.

      7.  SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS.  If a check for the
purchase price of any Shares tendered hereby is to be issued, or Share
Certificate(s) representing Shares not tendered or not purchased, including as a
result of proration, are to be issued, in the name of a person other than the
person(s) signing this Letter of Transmittal or if such check or any such Share
Certificate is to be sent to someone other than the person(s) signing this
Letter of Transmittal or to the person(s) signing this Letter of Transmittal but
at an address other than that shown in the box entitled "Description of Shares
Tendered" herein, the appropriate boxes in this Letter of Transmittal must be
completed. Stockholders delivering Shares tendered hereby by book-entry transfer
may request that Shares not purchased be credited to the account maintained at
the Book-Entry Transfer Facility as such stockholder may designate in the box
entitled "Special Payment Instructions" herein. If no such instructions are
given, all such Shares not purchased will be returned by crediting the same
account at the Book-Entry Transfer Facility as the account from which such
Shares were delivered.

      8.  WAIVER OF CONDITIONS.  Except as otherwise set forth in the Offer to
Purchase, the conditions of the Offer may be waived, in whole or in part, by
Purchaser, in its sole discretion, at any time and from time to time, in the
case of any Shares tendered. See Section 14 of the Offer to Purchase.

      9.  LOST, DESTROYED OR STOLEN CERTIFICATES.  If any Share Certificate(s)
have been lost, destroyed or stolen, the stockholder should promptly contact
EquiServe at 1-800-736-3001 for instructions as to the procedures for replacing
the Share Certificate(s). This Letter of Transmittal and related documents
cannot be processed until the lost, destroyed or stolen certificates have been
replaced and the replacement Share Certificates have been delivered to the
Depositary in accordance with the procedures set forth in Section 3 of the Offer
to Purchase and the instructions contained in this Letter of Transmittal.

      10.  QUESTIONS AND REQUESTS FOR ASSISTANCE OR ADDITIONAL
COPIES.  Questions and requests for assistance may be directed to the
Information Agent or the Dealer Manager at their respective addresses or
telephone numbers set forth below. Additional copies of the Offer to Purchase,
this Letter of Transmittal, the Notice of Guaranteed Delivery and the Guidelines
for Certification of Taxpayer Identification Number on Substitute Form W-9 may
be obtained from the Information Agent or the Dealer Manager or from brokers,
dealers, commercial banks or trust companies.

      11.  BACKUP WITHHOLDING; SUBSTITUTE FORM W-9; FORM W-8.  Each tendering
stockholder is required to provide the Depositary with a correct Taxpayer
Identification Number ("TIN") on the Substitute Form W-9 which is

                                        9
   10

provided under "Important Tax Information" below, and to certify, under
penalties of perjury, (1) that such number is correct, (2) that such stockholder
is not subject to backup withholding of Federal income tax and (3) that such
stockholder is a U.S. person. If a tendering stockholder has been notified by
the Internal Revenue Service that such stockholder is subject to backup
withholding, such stockholder must cross out item (2) of the Certification box
of the Substitute Form W-9, unless such stockholder has since been notified by
the Internal Revenue Service that such stockholder is no longer subject to
backup withholding. Failure to provide the requisite information on the
Substitute Form W-9 may subject the tendering stockholder to a $50 penalty
imposed by the Internal Revenue Service and to 31% Federal income tax
withholding on the payment of the purchase price of all Shares purchased from
such stockholder. If the tendering stockholder has not been issued a TIN and has
applied for one or intends to apply for one in the near future, such stockholder
should write "Applied For" in the space provided for the TIN in Part I of the
Substitute Form W-9, and sign and date the Substitute Form W-9 and the
Certificate of Awaiting Taxpayer Identification Number. If "Applied For" is
written in Part I and the Depositary is not provided with a TIN by the time of
the payment of purchase price to the tendering stockholder pursuant to the
Offer, the Depositary will withhold 31% on such payment. Each foreign
stockholder must complete and submit an appropriate Form W-8 in order to be
exempt from the 31% Federal income tax backup withholding due on payments with
respect to the Shares.

IMPORTANT: THIS LETTER OF TRANSMITTAL (OR FACSIMILE THEREOF), TOGETHER WITH ANY
REQUIRED SIGNATURE GUARANTEES, OR, IN THE CASE OF A BOOK-ENTRY TRANSFER, AN
AGENT'S MESSAGE, AND ANY OTHER REQUIRED DOCUMENTS, MUST BE RECEIVED BY THE
DEPOSITARY PRIOR TO THE EXPIRATION OF THE OFFER, AND EITHER SHARE CERTIFICATES
FOR TENDERED SHARES MUST BE RECEIVED BY THE DEPOSITARY OR SHARES MUST BE
DELIVERED PURSUANT TO THE PROCEDURES FOR BOOK-ENTRY TRANSFER, IN EACH CASE PRIOR
TO THE EXPIRATION DATE OF THE OFFER, OR THE TENDERING STOCKHOLDER MUST COMPLY
WITH THE PROCEDURES FOR GUARANTEED DELIVERY.

                           IMPORTANT TAX INFORMATION

      Under federal income tax law, a stockholder whose tendered Shares are
accepted for payment is required to provide the Depositary (as payer) with such
stockholder's correct TIN on Substitute Form W-9 below. If such stockholder is
an individual, the TIN is his or her social security number. If a tendering
stockholder is subject to backup withholding, such stockholder must cross out
item (2) of the Certification box on the Substitute Form W-9. If the Depositary
is not provided with the correct TIN, the stockholder may be subject to a $50
penalty imposed by the Internal Revenue Service. In addition, payments that are
made to such stockholder with respect to Shares purchased pursuant to the Offer
may be subject to backup withholding.

      Certain stockholders (including, among others, all corporations, and
certain foreign individuals) are not subject to these backup withholding and
reporting requirements. In order for a foreign individual to qualify as an
exempt recipient, that stockholder must submit an appropriate Form W-8
certifying to that individual's foreign status. Appropriate Forms W-8 can be
obtained from the Depositary. An exempt stockholder, other than a foreign
individual, should furnish its TIN, write "Exempt" on the face of the Substitute
Form W-9 below, and sign, date and return the Substitute Form W-9 to the
Depositary. See the enclosed Guidelines for Certification of Taxpayer
Identification Number on Substitute Form W-9 for additional instructions.

      If backup withholding applies, the Depositary is required to withhold 31%
of any payments made to the stockholder. Backup withholding is not an additional
tax. Rather, the federal income tax liability of persons subject to backup
withholding will be reduced by the amount of tax withheld. If backup withholding
results in an overpayment of taxes, a refund may be obtained from the Internal
Revenue Service.

PURPOSE OF SUBSTITUTE FORM W-9

      To prevent backup withholding on payments that are made to a stockholder
with respect to Shares purchased pursuant to the Offer, the stockholder is
required to notify the Depositary of such stockholder's correct TIN by
completing the Substitute Form W-9 contained herein and certifying that the TIN
provided on such form is correct (or that such stockholder is awaiting a TIN).

                                        10
   11

WHAT NUMBER TO GIVE THE DEPOSITARY

      The stockholder is required to give the Depositary the social security
number or employer identification number of the record owner of the Shares. If
the Shares are in more than one name or are not in the name of the actual owner,
consult the enclosed Guidelines for Certification of Taxpayer Identification
Number on Substitute Form W-9 for additional guidance on which number to report.
If the tendering stockholder has not been issued a TIN and has applied for a
number or intends to apply for a number in the near future, such stockholder
should write "Applied For" in the space provided for in the TIN in Part 1, and
sign and date the Substitute Form W-9. If "Applied For" is written in Part I and
the Depositary is not provided with a TIN by the time of payment, the Depositary
will withhold 31% on all payments of the purchase price, but if a certified TIN
is provided within 60 days, such amounts will be refunded.

                                        11
   12

                                                                                
- ---------------------------------------------------------------------------------------------------------------------------
                                        PAYER'S NAME: EQUISERVE TRUST COMPANY, N.A.
- ---------------------------------------------------------------------------------------------------------------------------
SUBSTITUTE                                                                            -------------------------------
 FORM W-9                       PART 1 -- PLEASE PROVIDE YOUR TIN IN THE BOX AT       Social Security Number
 DEPARTMENT OF THE TREASURY     RIGHT AND CERTIFY BY SIGNING AND DATING BELOW         (If awaiting TIN write "Applied For")
 INTERNAL REVENUE SERVICE
                                                                                      OR
                                                                                      -------------------------------
                                                                                      Employer Identification Number
                                                                                      (If awaiting TIN write "Applied For")
                               ------------------------------------------------------------------------------------------
                                PART 2 -- CERTIFICATION -- Under penalties of perjury, I certify that:
PAYER'S REQUEST FOR TAXPAYER    (1) The number shown on this form is my correct Taxpayer Identification Number (or I am
 IDENTIFICATION NUMBER          waiting for a number to be issued for me), and
     ("TIN")                    (2) I am not subject to backup withholding because: (a) I am exempt from backup
                                withholding, or (b) I have not been notified by the Internal Revenue Service (the "IRS")
                                    that I am subject to backup withholding as a result of a failure to report all interest
                                    or dividends, or (c) the IRS has notified me that I am no longer subject to backup
                                    withholding.
                                (3) I am a U.S. person (including a U.S. resident alien).
                               ------------------------------------------------------------------------------------------
                                CERTIFICATION INSTRUCTIONS -- You must cross out item (2) above if you have been notified
                                by the IRS that you are currently subject to backup withholding because of under-reporting
                                interest or dividends on your tax return. However, if after being notified by the IRS that
                                you are subject to backup withholding, you receive another notification from the IRS that
                                you are no longer subject to backup withholding, do not cross out item (2). (Also see
                                instructions in the enclosed Guidelines).
                               ------------------------------------------------------------------------------------------

                                SIGNATURE: ------------------  DATE:-------- , 2001   PART 3 -- Check if you are
                                                                                      awaiting TIN  [ ]
- ---------------------------------------------------------------------------------------------------------------------------

NOTE:  FAILURE TO COMPLETE AND RETURN ONE OF THESE FORMS MAY RESULT IN BACKUP
       WITHHOLDING OF 31% OF ANY CASH PAYMENTS MADE TO YOU PURSUANT TO THE
       OFFER. PLEASE REVIEW THE ENCLOSED GUIDELINES FOR CERTIFICATION OF
       TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL
       DETAILS.

       YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU CHECKED THE BOX IN
       PART 3 OF THE SUBSTITUTE FORM W-9.

             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

     I certify under penalties of perjury that a Taxpayer Identification Number
has not been issued to me, and either (1) I have mailed or delivered an
application to receive a Taxpayer Identification Number to the appropriate
Internal Revenue Service Center or Social Security Administration Office or (2)
I intend to mail or deliver an application in the near future. I understand that
if I do not provide a Taxpayer Identification Number to the Depositary by the
time of payment, 31% of all reportable payments made to me thereafter will be
withheld, but that such amounts will be refunded to me if I provide a certified
Taxpayer Identification Number to the Depositary within sixty (60) days.

Signature:
- -------------------------------------------------------------------  Date:
- ------------------------ , 2001

                                        12
   13

      Questions and requests for assistance or additional copies of the Offer to
Purchase, this Letter of Transmittal and other tender offer materials may be
directed to the Information Agent or the Dealer Manager as set forth below:

                    The Information Agent for the Offer is:

                                [GEORGESON LOGO]
                          17 State Street, 10th Floor
                               New York, NY 10004
                 BANKS AND BROKERS CALL COLLECT (212) 440-9800
                    ALL OTHERS CALL TOLL FREE (800) 223-2064

                      The Dealer Manager for the Offer is:

                              MERRILL LYNCH & CO.
                          Four World Financial Center
                            New York, New York 10080
                          Call Collect: (212) 236-3790
   1
                                                                 Exhibit (a)(3)

                         NOTICE OF GUARANTEED DELIVERY

                      FOR TENDER OF SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       TO

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)

      This Notice of Guaranteed Delivery (or one substantially in the form
hereof) must be used to accept the Offer (as defined below) if (a) certificates
("Share Certificates") representing shares of common stock, par value $0.01 per
share (including the associated Rights (as defined below), the "Shares"), of
Barrett Resources Corporation, a Delaware corporation ("Barrett Resources"), are
not immediately available or time will not permit all required documents to
reach EquiServe Trust Company, N.A. (the "Depositary") on or prior to the
Expiration Date (as defined in the Offer to Purchase described below); or (b)
the procedure for book-entry transfer, as set forth in the Offer to Purchase,
cannot be completed on a timely basis. As used herein, "Rights" means the
preferred stock purchase rights associated with the Shares and issued pursuant
to the Rights Agreement, dated as of August 5, 1997, between Barrett Resources
and Fleet National Bank, as successor to BankBoston, N.A., as Rights Agent, as
amended (the "Rights Agreement"). Unless the context otherwise requires, all
references to Shares shall be deemed to include the associated Rights, and all
references to the Rights shall be deemed to include the benefits that may inure
to holders of the Rights pursuant to the Rights Agreement. This Notice of
Guaranteed Delivery may be delivered by hand or mail or transmitted by facsimile
transmission to the Depositary. See Section 3 of the Offer to Purchase.

                        The Depositary for the Offer is:

                         EQUISERVE TRUST COMPANY, N.A.

            By Mail:                     By Overnight Courier:                    By Hand:
                                                                
     Attn: Corporate Actions            Attn: Corporate Actions            Attn: Corporate Actions
         P.O. Box 43025                   40 Campanelli Drive          Securities Transfer & Reporting
    Providence, RI 02940-3025             Braintree, MA 02184                  Services, Inc.
                                                                                c/o EquiServe
                                                                        100 William Street, Galleria
                                                                             New York, NY 10038
                                             By Facsimile:
                                   (for Eligible Institutions only)
                                            (781) 575-4826
                                    Confirm Facsimile By Telephone:
                                            (781) 575-4816

      DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE, OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE TO A NUMBER OTHER
THAN AS LISTED ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY.

      THIS NOTICE OF GUARANTEED DELIVERY IS NOT TO BE USED TO GUARANTEE
SIGNATURES. IF A SIGNATURE ON A LETTER OF TRANSMITTAL IS REQUIRED TO BE
GUARANTEED BY AN "ELIGIBLE INSTITUTION" UNDER THE INSTRUCTIONS THERETO, SUCH
SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE SPACE PROVIDED IN THE
SIGNATURE BOX IN THE LETTER OF TRANSMITTAL.

                 THE GUARANTEE ON THE REVERSE SIDE MUST BE COMPLETED
   2

Ladies and Gentlemen:

      The undersigned hereby tenders to Resources Acquisition Corp., a Delaware
corporation, upon the terms and subject to the conditions set forth in the Offer
to Purchase dated May 14, 2001 (the "Offer to Purchase") and the related Letter
of Transmittal (which, as amended or supplemented from time to time, together
constitute the "Offer"), receipt of each of which is hereby acknowledged, the
number of Shares indicated below pursuant to the guaranteed delivery procedures
set forth in Section 3 of the Offer to Purchase:

          ------------------------------------------------------------

   Name(s) of Record Holder(s)

          ------------------------------------------------------------

          ------------------------------------------------------------

          ------------------------------------------------------------

   Address(es)

          ------------------------------------------------------------

          ------------------------------------------------------------
                                                                     ZIP CODE

   (Area Code) Telephone No.
   ---------------------------

                                       X
            --------------------------------------------------------

                                       X
            --------------------------------------------------------
                        SIGNATURE(S) OF RECORD HOLDER(S)

- ------------------------------------------------------------
          ------------------------------------------------------------

   Number of Shares
   ---------------------------------------

   Certificate No.(s) (if available)
   -------------------------

   Indicate account number at Book-Entry Transfer Facility if Shares will be
   tendered by book-entry transfer:

   Account Number
   ----------------------------------------

   Dated:
   ------------------------ , 2001

- ------------------------------------------------------------

                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)

      The undersigned, a bank, broker, dealer, credit union, savings association
or other entity that is a member in good standing of the Securities Transfer
Agents Medallion Program (an "Eligible Institution"), hereby (a) represents that
the above named person(s) "own(s)" the Shares tendered hereby within the meaning
of Rule 14e-4 of the Securities Exchange Act of 1934, as amended ("Rule 14e-4"),
(b) represents that such tender of Shares complies with Rule 14e-4 and (c)
guarantees delivery to the Depositary, at one of its addresses set forth above,
of either the Share Certificates evidencing all Shares tendered hereby in proper
form for transfer, or confirmation of the book-entry transfer of Shares into the
Depositary's account at The Depository Trust Company, in either case together
with delivery of a properly completed and duly executed Letter of Transmittal
(or facsimile thereof) with any required signature guarantee, or an Agent's
Message (as defined in the Offer to Purchase) in connection with a book-entry
delivery, and any other documents required by the Letter of Transmittal, within
three (3) New York Stock Exchange trading days after the date of execution of
this Notice of Guaranteed Delivery.

      The Eligible Institution that completes this form must communicate the
guarantee to the Depositary and must deliver the Letter of Transmittal and Share
Certificates to the Depositary within the time period indicated herein. Failure
to do so may result in financial loss to such Eligible Institution.

                                                
Name of Firm
  ------------------------------------------       X
                                                   -----------------------------------------------
                                                   AUTHORIZED SIGNATURE
Address                                            Name
- -----------------------------------------------    -----------------------------------------------
                                                   (PLEASE PRINT OR TYPE)
                                                   Title
- -----------------------------------------------    -----------------------------------------------
ZIP CODE
(Area Code)                                        Dated:
                                                   ------------------------------------------, 2001
Telephone No.
  ------------------------------------------

NOTE:  DO NOT SEND CERTIFICATES FOR SHARES OR RIGHTS WITH THIS NOTICE.
       CERTIFICATES FOR SHARES OR RIGHTS SHOULD BE SENT WITH YOUR LETTER OF
       TRANSMITTAL

                                        2
   1
                                                                Exhibit (a)(4)

[MERRILL LYNCH LOGO]
Four World Financial Center
New York, New York 10080
                           OFFER TO PURCHASE FOR CASH

                       16,730,502 SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       AT

                              $73.00 NET PER SHARE

                                       BY

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.

      THE OFFER, PRORATION PERIOD AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00
MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11, 2001, UNLESS THE OFFER IS EXTENDED.

                                                                    May 14, 2001
To Brokers, Dealers, Commercial Banks,
  Trust Companies and Other Nominees:

      We have been appointed by Resources Acquisition Corp., a Delaware
corporation ("Purchaser") and a wholly-owned subsidiary of The Williams
Companies, Inc., a Delaware corporation ("Williams"), to act as Dealer Manager
in connection with Purchaser's offer to purchase 16,730,502 shares of common
stock, par value $0.01 per share (including the associated Rights (as defined
below), the "Shares") of Barrett Resources Corporation, a Delaware corporation
("Barrett Resources"), at a purchase price of $73.00 per Share, net to the
seller in cash, without interest, upon the terms and subject to the conditions
set forth in the Offer to Purchase dated May 14, 2001 (the "Offer to Purchase")
and in the related Letter of Transmittal (which, as amended or supplemented from
time to time, together constitute the "Offer") enclosed herewith. As used
herein, "Rights" means the preferred stock purchase rights (the "Rights")
associated with the Shares and issued under the Rights Agreement (the "Rights
Agreement") dated as of August 5, 1997 by and between Barrett Resources and
Fleet National Bank, as successor to BankBoston, N.A., as Rights Agent, as
amended. Unless the content otherwise requires, all references to the Shares
shall be deemed to include the Rights, and all references to the Rights shall be
deemed to include the benefits that may inure to holders of the Rights pursuant
to the Rights Agreement.

      If a stockholder desires to tender Shares pursuant to the Offer and such
stockholder's Share certificates are not immediately available or time will not
permit all required documents to reach the Depositary prior to the Expiration
Date (as defined in the Offer to Purchase) of the Offer or the procedures for
book-entry transfer cannot be completed on a timely basis, such Shares may
nevertheless be tendered according to the guaranteed delivery procedures set
forth in Section 3 of the Offer to Purchase. See Instruction 2 of the Letter of
Transmittal. Delivery of documents to the Book-Entry Transfer Facility (as
defined in the Offer to Purchase) in accordance with the Book-Entry Transfer
Facility's procedures does not constitute delivery to the Depositary.

      Please furnish copies of the enclosed materials to those of your clients
for whose accounts you hold Shares registered in your name or in the name of
your nominee.
   2

      The Offer is conditioned upon, among other things, (i) there being validly
tendered and not properly withdrawn prior to the expiration date of the Offer at
least 16,730,502 Shares on the date Shares are accepted for payment and (ii) the
expiration or termination of the waiting period under the Hart-Scott-Rodino
Antitrust Improvements Act of 1976, as amended, and the rules and regulations
promulgated thereunder. The Offer is not subject to a financing condition. The
Offer is also subject to the other conditions set forth in the Offer to
Purchase. See the Introduction and Section 14 of the Offer to Purchase.

      THE BOARD OF DIRECTORS OF BARRETT RESOURCES HAS UNANIMOUSLY APPROVED THE
OFFER, THE MERGER (AS DEFINED BELOW), AND THE MERGER AGREEMENT (AS DEFINED
BELOW), HAS DETERMINED THAT THE TERMS OF EACH ARE ADVISABLE, FAIR TO, AND IN THE
BEST INTERESTS OF, THE STOCKHOLDERS OF BARRETT RESOURCES, AND RECOMMENDS THAT
STOCKHOLDERS ACCEPT THE OFFER AND TENDER THEIR SHARES PURSUANT TO THE OFFER AND
APPROVE THE MERGER AT THE TIME OF BARRETT RESOURCES' STOCKHOLDER MEETING.

      The Offer is being made pursuant to an Agreement and Plan of Merger, dated
as of May 7, 2001 (the "Merger Agreement"), by and among Williams, Purchaser and
Barrett Resources, pursuant to which, following the consummation of the Offer
and in accordance with the Delaware General Corporation Law, and subject to the
satisfaction or waiver of certain conditions, including approval of stockholders
of Barrett Resources, Barrett Resources will merge with and into Purchaser with
Purchaser continuing as the surviving corporation, unless certain conditions
related to the United States federal income tax treatment of the Offer and the
Merger of Barrett Resources with and into Purchaser are not satisfied, in which
case Purchaser will merge with and into Barrett Resources with Barrett Resources
as the surviving corporation (collectively, the "Merger"). In the Merger,
stockholders of Barrett Resources will exchange each of their Shares for 1.767
shares of Williams common stock, par value $1.00 per share, with cash in lieu of
fractional shares. The exchange ratio of 1.767 shares of Williams common stock
per Share is a fixed ratio that will not be adjusted as a result of any increase
or decrease in the market price of either shares of Williams common stock or
Barrett Resources Shares. The market price of shares of Williams common stock at
the time the Merger is completed may therefore be higher or lower than their
price on the date of this document and on the date of the special meeting of
stockholders to be held to vote on the Merger. As a result, the Williams common
stock you as a Barrett Resources stockholder would receive in the Merger may be
worth more or less than the price being offered for the Shares in the Offer. WE
URGE YOU TO OBTAIN CURRENT MARKET QUOTATIONS FOR BOTH BARRETT RESOURCES SHARES
AND SHARES OF WILLIAMS COMMON STOCK BEFORE DECIDING WHETHER TO TENDER YOUR
SHARES. Section 11 of the Offer to Purchase contains a more detailed description
of the Merger Agreement, the Offer, the Merger and the consideration payable in
the Merger in respect of the Shares.

      Enclosed herewith for your information and forwarding to your clients are
copies of the following documents:

             1. The Offer to Purchase dated May 14, 2001.

             2. The Letter of Transmittal for your use to tender Shares and for
      the information of your clients. Facsimile copies of the Letter of
      Transmittal may be used to tender Shares.

             3. A printed form of letter which may be sent to your clients for
      whose accounts you hold Shares registered in your name or in the name of
      your nominee, with space provided for obtaining such clients' instructions
      with regard to the Offer.

             4. The Notice of Guaranteed Delivery for Shares to be used to
      accept the Offer if certificates for Shares ("Share Certificates") and all
      other required documents are not immediately available or cannot be
      delivered to EquiServe Trust Company, N.A. (the "Depositary") by the
      Expiration Date or if the procedure for book-entry transfer cannot be
      completed by the Expiration Date.

             5. A letter to stockholders from Peter Dea, the Chairman of the
      Board of Directors of Barrett Resources, accompanied by Barrett Resources'
      Solicitation/Recommendation Statement on Schedule 14D-9.

             6. Guidelines of the Internal Revenue Service for Certification of
      Taxpayer Identification Number on Substitute Form W-9.

             7. A return envelope addressed to the Depositary.

      YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER, PRORATION PERIOD AND WITH-

                                        2
   3

DRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11,
2001, UNLESS THE OFFER IS EXTENDED.

      In order to accept the Offer, a duly executed and properly completed
Letter of Transmittal and any required signature guarantees, or an Agent's
Message (as defined in the Offer to Purchase) in connection with a book-entry
delivery of Shares, and any other required documents should be sent to the
Depositary and either Share Certificates representing the tendered Shares should
be delivered to the Depositary, or Shares should be tendered by book-entry
transfer into the Depositary's account maintained at the Book Entry Transfer
Facility (as defined in the Offer to Purchase), all in accordance with the
instructions set forth in the Letter of Transmittal and the Offer to Purchase.

      If holders of Shares wish to tender, but it is impracticable for them to
forward their Share Certificates or other required documents on or prior to the
Expiration Date or to comply with the book-entry transfer procedures on a timely
basis, a tender may be effected by following the guaranteed delivery procedures
specified in Section 3 of the Offer to Purchase.

      Purchaser will not pay any commissions or fees to any broker, dealer or
other person (other than the Dealer Manager and the Information Agent) for
soliciting tenders of Shares pursuant to the Offer. Purchaser will, however,
upon request, reimburse you for customary clerical and mailing expenses incurred
by you in forwarding any of the enclosed materials to your clients. Purchaser
will pay or cause to be paid any stock transfer taxes applicable to its purchase
of Shares pursuant to the Offer, except as otherwise provided in Instruction 6
of the Letter of Transmittal.

      Any inquiries you may have with respect to the Offer should be addressed
to, and additional copies of the enclosed material may be obtained from, the
Information Agent or the Dealer Manager at their respective addresses and
telephone numbers set forth on the back cover of the Offer to Purchase.

                                      Very truly yours,

                                      Merrill Lynch & Co.

      NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
OR ANY OTHER PERSON THE AGENT OF PURCHASER, BARRETT RESOURCES, THE DEALER
MANAGER, THE DEPOSITARY OR THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF
THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY STATEMENT OR USE ANY
DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER OTHER THAN THE
ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.

                                        3
   1
                                                                 Exhibit (a)(5)

                           OFFER TO PURCHASE FOR CASH

                       16,730,502 SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       AT

                              $73.00 NET PER SHARE

                                       BY

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.

     THE OFFER, PRORATION PERIOD AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00
MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11, 2001, UNLESS THE OFFER IS EXTENDED.

                                                                    May 14, 2001

To Our Clients:

      Enclosed for your consideration are the Offer to Purchase dated May 14,
2001 (the "Offer to Purchase") and the related Letter of Transmittal (which, as
amended or supplemented from time to time, together constitute the "Offer") in
connection with the offer by Resources Acquisition Corp., a Delaware corporation
("Purchaser") and a wholly-owned subsidiary of The Williams Companies, Inc., a
Delaware corporation ("Williams"), to purchase 16,730,502 shares of common
stock, par value $0.01 per share (including the associated Rights (as defined
below), the "Shares") of Barrett Resources Corporation, a Delaware corporation
("Barrett Resources"), at a purchase price of $73.00 per Share, net to the
seller in cash, without interest, upon the terms and subject to the conditions
set forth in the Offer to Purchase. As used herein, "Rights" means the preferred
stock purchase rights associated with the Shares and issued under the Rights
Agreement (the "Rights Agreement") dated as of August 5, 1997 by and between
Barrett Resources and Fleet National Bank, as successor to BankBoston, N.A., as
Rights Agent, as amended. Unless the content otherwise requires, all references
to the shares shall be deemed to include the Rights, and all references to the
Rights shall be deemed to include the benefits that may inure to holders of the
Rights pursuant to the Rights Agreement.

      If a stockholder desires to tender Shares pursuant to the Offer and such
stockholder's Share certificates are not immediately available or time will not
permit all required documents to reach the Depositary prior to the Expiration
Date (as defined in the Offer to Purchase) or the procedures for book-entry
transfer cannot be completed on a timely basis, such Shares may nevertheless be
tendered according to the guaranteed delivery procedures set forth in Section 3
of the Offer to Purchase. See Instruction 2 of the Letter of Transmittal.
Delivery of documents to the Book-Entry Transfer Facility (as defined in the
Offer to Purchase) in accordance with the Book-Entry Transfer Facility's
procedures does not constitute delivery to the Depositary.

      WE ARE THE HOLDER OF RECORD OF SHARES HELD BY US FOR YOUR ACCOUNT. A
TENDER OF SUCH SHARES CAN BE MADE ONLY BY US AS THE HOLDER OF RECORD AND
PURSUANT TO YOUR INSTRUCTIONS. THE ENCLOSED LETTER OF TRANSMITTAL IS FURNISHED
TO YOU FOR YOUR INFORMATION ONLY AND CANNOT BE USED BY YOU TO TENDER SHARES HELD
BY US FOR YOUR ACCOUNT.
   2

      ACCORDINGLY, WE REQUEST INSTRUCTIONS AS TO WHETHER YOU WISH TO HAVE US
TENDER ON YOUR BEHALF ANY OR ALL SHARES HELD BY US FOR YOUR ACCOUNT PURSUANT TO
THE TERMS AND CONDITIONS SET FORTH IN THE OFFER.

      Please note the following:

             1. The tender price is $73.00 per Share, net to you in cash,
      without interest, upon the terms and subject to the conditions set forth
      in the Offer.

             2. The Offer is being made for 16,730,502 Shares (representing
      approximately 50% of the outstanding Shares). If more than 16,730,502
      Shares are tendered, Purchaser will purchase 16,730,502 of such tendered
      Shares on a pro rata basis.

             3. The Board of Directors of Barrett Resources has unanimously
      approved the Offer, the Merger (as defined below), and the Merger
      Agreement (as defined below), determined that the terms of each are
      advisable, fair to, and in the best interests of, the stockholders of
      Barrett Resources, and recommends that Barrett Resources' stockholders
      accept the Offer and tender their Shares pursuant to the Offer and approve
      the Merger at the time of Barrett Resources' stockholder meeting.

             4. The Offer is being made pursuant to an Agreement and Plan of
      Merger, dated as of May 7, 2001 (the "Merger Agreement"), by and among
      Williams, Purchaser and Barrett Resources, pursuant to which, following
      the consummation of the Offer and in accordance with the Delaware General
      Corporation Law, and subject to the satisfaction or waiver of certain
      conditions, including approval of stockholders of Barrett Resources,
      Barrett Resources will merge with and into Purchaser with Purchaser
      continuing as the surviving corporation, unless certain conditions related
      to taxes are not satisfied, in which case Purchaser will merge with and
      into Barrett Resources with Barrett Resources as the surviving corporation
      (collectively, the "Merger"). In the Merger, stockholders of Barrett
      Resources will exchange each of their Shares for 1.767 shares of Williams
      common stock, par value $1.00 per share, with cash in lieu of fractional
      shares. The exchange ratio of 1.767 shares of Williams common stock per
      Share is a fixed ratio that will not be adjusted as a result of any
      increase or decrease in the market price of either shares of Williams
      common stock or Shares of Barrett Resources. The market price of shares of
      Williams common stock at the time the Merger is completed may therefore be
      higher or lower than their price on the date of this document, the date of
      the consummation of the Offer and on the date of the special meeting of
      stockholders to be held to vote on the Merger. As a result, the Williams
      common stock you as a Barrett Resources stockholder may receive in the
      Merger may be worth more or less than the price being offered for the
      Shares in the Offer. WE URGE YOU TO OBTAIN CURRENT MARKET QUOTATIONS FOR
      BOTH SHARES OF BARRETT RESOURCES AND SHARES OF WILLIAMS COMMON STOCK
      BEFORE DECIDING WHETHER TO TENDER YOUR SHARES. Section 11 of the Offer to
      Purchase contains a more detailed description of the Merger Agreement, the
      Offer, the Merger and the consideration payable in the Merger in respect
      of the Shares.

             5. The Offer is conditioned upon, among other things, (i) there
      being validly tendered and not properly withdrawn prior to the Expiration
      Date of the Offer at least 16,730,502 Shares and (ii) the expiration or
      termination of the waiting periods under the Hart-Scott-Rodino Antitrust
      Improvements Act of 1976, as amended, and the rules and regulations
      promulgated thereunder. The Offer is not subject to a financing condition.
      The Offer is also subject to the other conditions set forth in the Offer
      to Purchase. See the Introduction and Section 14 of the Offer to Purchase.

             6. Any stock transfer taxes applicable to the sale of Shares to
      Purchaser pursuant to the Offer will be paid by Purchaser, except as
      otherwise provided in Instruction 6 of the Letter of Transmittal.

             7. The Offer, proration period and withdrawal rights will expire at
      12:00 Midnight, eastern time, on Monday, June 11, 2001, unless the Offer
      is extended.

             8. Payment for Shares purchased pursuant to the Offer will in all
      cases be made only after timely receipt by the Depositary of (a) Share
      Certificates or timely confirmation of the book-entry transfer of such
      Shares into the account maintained by the Book-Entry Transfer Facility (as
      defined in the Offer to Purchase), pursuant to the procedures set forth in
      Section 3 of the Offer to Purchase, (b) the Letter of Transmittal (or a
      facsimile thereof), properly completed and duly executed, with any
      required signature guarantees or an Agent's Message (as defined in the
      Offer to Purchase), in connection with a book-entry delivery and (c) any
      other

                                        2
   3

      documents required by the Letter of Transmittal. Accordingly, payment may
      not be made to all tendering stockholders at the same time, depending upon
      when Share Certificates or confirmations of book-entry transfer of such
      Shares into the Depositary's account at the Book-Entry Transfer Facility
      are actually received by the Depositary.

      If you wish to have us tender any or all of the Shares held by us for your
account, please so instruct us by completing, executing, detaching and returning
to us the instruction form set forth on the back page of this letter. If you
authorize the tender of your Shares, all such Shares will be tendered unless
otherwise specified on the back page of this letter. An envelope to return your
instructions to us is enclosed. YOUR INSTRUCTIONS SHOULD BE FORWARDED TO US IN
AMPLE TIME TO PERMIT US TO SUBMIT A TENDER ON YOUR BEHALF PRIOR TO THE
EXPIRATION OF THE OFFER.

      Purchaser is not aware of any state where making the Offer is prohibited
by any applicable law. If Purchaser becomes aware of any applicable law
prohibiting the making of the Offer or the acceptance of the Shares pursuant
thereto, Purchaser will make a good faith effort to comply with such law or seek
to have such law declared inapplicable to the Offer. If, after such good faith
effort, Purchaser cannot comply with such state statute, the Offer will not be
made (nor will tenders be accepted from or on behalf of) holders of Shares in
such state. In any jurisdiction where the securities, blue sky or other laws
require the Offer to be made by a licensed broker or dealer, the Offer will be
deemed to be made on behalf of the Purchaser by Merrill Lynch & Co. (the Dealer
Manager), or by one or more registered brokers or dealers that are licensed
under the laws of such jurisdiction.

                                        3
   4

          INSTRUCTIONS WITH RESPECT TO THE OFFER TO PURCHASE FOR CASH

                       16,730,502 SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                       OF

                         BARRETT RESOURCES CORPORATION
                                       AT

                              $73.00 NET PER SHARE

                                       BY

                          RESOURCES ACQUISITION CORP.,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          THE WILLIAMS COMPANIES, INC.

      The undersigned acknowledge(s) receipt of your letter, the enclosed Offer
to Purchase dated May 14, 2001 (the "Offer to Purchase") and the related Letter
of Transmittal (which, as amended or supplemented from time to time, together
constitute the "Offer") in connection with Purchaser's offer to purchase
16,730,502 shares of common stock, par value $0.01 per share (including the
associated preferred stock purchase rights, the "Shares") of Barret Resources
Corporation, a Delaware corporation.

      This will instruct you to tender the number of Shares indicated below (or
if no number is indicated below, all Shares) which are held by you for the
account of the undersigned, upon the terms and subject to the conditions set
forth in the Offer.

Number of Shares to be Tendered:
- ------------------------------ Shares*

                                   SIGN BELOW

Account Number:
- ------------------------------  Signature(s)
- ------------------------------------------------------

Dated:
- ------------------------------------, 2001

- --------------------------------------------------------------------------------
                          PLEASE TYPE OR PRINT NAME(S)

- --------------------------------------------------------------------------------
                     PLEASE TYPE OR PRINT ADDRESS(ES) HERE

- --------------------------------------------------------------------------------
                       AREA CODE AND TELEPHONE NUMBER(S)

- --------------------------------------------------------------------------------
              TAXPAYER IDENTIFICATION OR SOCIAL SECURITY NUMBER(S)

- ---------------
* Unless otherwise indicated, it will be assumed that you instruct us to tender
  all Shares held by us for your account.

                                        4
   1
                                                                 Exhibit (a)(6)

                    GUIDELINES FOR CERTIFICATION OF TAXPAYER
                  IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9

GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYER -- Social Security numbers have nine digits separated by two hyphens: i.e.
000-00-0000. Employer identification numbers have nine digits separated by only
one hyphen: i.e. 00-0000000. The table below will help determine the number to
give the payer.

- ------------------------------------------------------------
                                              GIVE THE
                                           SOCIAL SECURITY
       FOR THIS TYPE OF ACCOUNT:            NUMBER OF --
- ------------------------------------------------------------
                                   
 1.  An individual's account             The individual

 2.  Two or more individuals (joint      The actual owner of
     account)                            the account or, if
                                         combined funds, the
                                         first individual on
                                         the account(1)

 3.  Custodian account of a minor        The minor(2)
     (Uniform Gift to Minors Act)

 4.  a. The usual revocable savings      The grantor-
        trust account (grantor is also   trustee(1)
        trustee)

     b. So-called trust account that is  The actual owner(1)
        not a legal or valid trust
        under State law

 5.  Sole proprietorship account         The owner(3)
- ------------------------------------------------------------

- ------------------------------------------------------------
                                          GIVE THE EMPLOYER
                                           IDENTIFICATION
       FOR THIS TYPE OF ACCOUNT:            NUMBER OF --
- ------------------------------------------------------------
                                   
 6.  A valid trust, estate, or pension   Legal entity (Do
     trust                               not furnish the
                                         identifying number
                                         of the personal
                                         representative or
                                         trustee unless the
                                         legal entity itself
                                         is not designated
                                         in the account
                                         title).(4)

 7.  Corporate account                   The corporation

 8.  Association, club, religious,       The organization
     charitable, educational or other
     tax-exempt organization account

 9.  Partnership account held in the     The partnership
     name of the business

10.  A broker or registered nominee      The broker or
                                         nominee

11.  Account with the Department of      The public entity
     Agriculture in the name of a
     public entity (such as a State or
     local government, school district
     or prison) that receives
     agricultural program payments
- ------------------------------------------------------------

(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's Social Security number.
(3) You must show your individual name, but you may also enter your business or
    "doing business as" name. You may use either your Social Security number or
    employer identification number.
(4) List first and circle the name of the legal trust, estate, or pension trust.

NOTE: If no name is circled when there is more than one name, the number will be
      considered to be that of the first name listed.

RESIDENT ALIEN INDIVIDUALS: If you are a resident alien individual and you do
not have, and are not eligible to get, a Social Security number, your taxpayer
identification number is your individual taxpayer identification number ("ITIN")
as issued by the Internal Revenue Service. Enter it on the portion of the
Substitute Form W-9 where the Social Security number would otherwise be entered.
If you do not have an ITIN, see "How to Obtain a TIN" below.
   2

            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

                                     PAGE 2

HOW TO OBTAIN A TIN
If you don't have a taxpayer identification number ("TIN") or you don't know
your number, obtain Form SS-5, Application for a Social Security number, or Form
SS-4, Application for Employer Identification Number, at the local office of the
Social Security Administration or the Internal Revenue Service (the "IRS") and
apply for a number. Resident alien individuals who are not eligible to get a
Social Security number and need an ITIN should obtain Form W-7, Application for
Individual Taxpayer Identification Number, from the IRS.

PAYEES AND PAYMENTS EXEMPT FROM BACKUP WITHHOLDING
Payees specifically exempted from backup withholding on all payments include the
following:
  - An organization exempt from tax under section 501(a), any IRA, or a
    custodial account under section 403(b)(7), if the account satisfies the
    requirements of section 401(f)(2).
  - The United States or any of its agencies or instrumentalities.
  - A state, the District of Columbia, a possession of the United States, or any
    of their political subdivisions or instrumentalities.
  - A foreign government or any of its political subdivisions, agencies, or
    instrumentalities.
  - An international organization or any of its agencies or instrumentalities.
  Other payees that MAY BE EXEMPT from backup withholding include:
  - A corporation.
  - A foreign central bank of issue.
  - A dealer in securities or commodities required to register in the United
    States, the District of Columbia, or a possession of the United States.
  - A real estate investment trust.
  - An entity registered at all times during the tax year under the Investment
    Company Act of 1940.
  - A common trust fund operated by a bank under section 584(a).
  - A financial institution.
  - A middleman known in the investment community as a nominee or custodian.
  - A trust exempt from tax under section 664 or described in section 4947.
  Payments of dividends not generally subject to backup withholding include the
following:
  - Payments to nonresident aliens subject to withholding under section 1441.
  - Payments to partnerships not engaged in a trade or business in the United
    States and that have at least one nonresident alien partner.
  - Payments of patronage dividends not paid in money.
  - Payments made by certain foreign organizations.
  - Section 401(k) distributions made by an ESOP.
  Payments of interest not generally subject to backup withholding include the
following:
  - Payments of interest on obligations issued by individuals.
NOTE:  You may be subject to backup withholding if this interest is $600 or more
and is paid in the course of the payer's trade of business and you have not
provided your correct taxpayer identification number to the payer.
  - Payments of tax-exempt interest (including exempt-interest dividends under
    section 852).
  - Payments described in section 6049(b)(5) to nonresident aliens.
  - Payments on tax-free covenant bonds under section 1451.
  - Payments made by certain foreign organizations.
  Exempt payees described above should file Substitute Form W-9 with the payer
to avoid possible erroneous backup withholding. FURNISH YOUR TAXPAYER
IDENTIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM IN PART II, SIGN
AND DATE THE FORM, AND RETURN IT TO THE PAYER.
  Certain payments, other than interest, dividends and patronage dividends, that
are not subject to information reporting are also not subject to backup
withholding. For details, see sections 6041, 6041A, 6042, 6044, 6045, 6049,
6050A and 6050N and the Treasury regulations under these sections.

PRIVACY ACT NOTICE. -- Section 6109 requires most recipients of dividend,
interest or other payments to give their correct TINs to payers who must report
the payments to the IRS. The IRS uses the numbers for identification purposes
and to help verify the accuracy of tax returns. Payers must be given the numbers
whether or not recipients are required to file tax returns. Payers must
generally withhold 31% of taxable interest, dividend and certain other payments
to a payee who does not furnish a TIN to a payer. Certain penalties may also
apply.

PENALTIES
(1) FAILURE TO FURNISH TIN. -- If you fail to furnish your correct TIN to a
payer, you are subject to a penalty of $50 for each such failure unless your
failure is due to reasonable cause and not to willful neglect.
(2) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING. -- If you
make a false statement with no reasonable basis that results in no imposition of
backup withholding, you are subject to a $500 penalty.
(3) CRIMINAL PENALTY FOR FALSIFYING INFORMATION. -- Willfully falsifying
certifications or affirmations may subject you to criminal penalties including
fines and/or imprisonment.

       FOR ADDITIONAL INFORMATION CONTACT YOUR TAX CONSULTANT OR THE IRS.
   1

                                                                  Exhibit (a)(8)

This announcement is neither an offer to purchase nor a solicitation of an offer
to sell Shares (as defined below). The Offer (as defined below) is made only by
the Offer to Purchase dated May 14, 2001 and the related Letter of Transmittal
and any amendments or supplements thereto, and is being made to all holders of
Shares. Purchaser (as defined below) is not aware of any state where the making
of the Offer is prohibited by any applicable law. If Purchaser becomes aware of
any applicable law prohibiting the making of the Offer or the acceptance of
the Shares pursuant thereto, Purchaser will make a good faith effort to comply
with such law or seek to have such law declared inapplicable to the Offer. If,
after such good faith effort, Purchaser cannot comply with such state statute,
the Offer will not be made (nor will tenders be accepted from or on behalf of)
holders of Shares in such state. In any jurisdiction where the securities, blue
sky or other laws require the Offer to be made by a licensed broker or dealer,
the Offer will be deemed to be made on behalf of the Purchaser by Merrill Lynch
& Co., as Dealer Manager (as defined below), or by one or more registered
brokers or dealers that are licensed under the laws of such jurisdiction.

NOTICE OF OFFER TO PURCHASE FOR CASH
16,730,502 SHARES OF COMMON STOCK
(INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
OF
BARRETT RESOURCES CORPORATION
AT
$73.00 NET PER SHARE
BY
RESOURCES ACQUISITION CORP.,
A WHOLLY OWNED SUBSIDIARY OF
THE WILLIAMS COMPANIES, INC.

Resources Acquisition Corp., a Delaware corporation ("Purchaser") and a
wholly-owned subsidiary of The Williams Companies, Inc., a Delaware corporation
("Williams"), is offering to purchase 16,730,502 shares of common stock, par
value $0.01 per share (including the associated Barrett Resources Rights (as
defined in the Offer to Purchase), the "Shares"), of Barrett Resources
Corporation, a Delaware corporation (the "Company"), at a purchase price of
$73.00 per Share, net to the seller in cash, without interest thereon (the
"Offer Price"), upon the terms and subject to the conditions set forth in the
Offer to Purchase dated May 14, 2001 (the "Offer to Purchase") and in the
related Letter of Transmittal (which, together with any amendments or
supplements thereto, collectively constitute the "Offer"). Tendering
stockholders who have Shares registered in their names and who tender directly
to EquiServe Trust Company, N.A. (the "Depositary") will not be charged
brokerage fees or commissions or, subject to Instruction 6 of the Letter of
Transmittal, transfer taxes on the purchase of Shares pursuant to the Offer.
Stockholders who hold their Shares through a broker or bank should consult such
institution as to whether it charges any service fees. Purchaser will pay all
charges and expenses of the Depositary, Merrill Lynch & Co., which is acting as
the dealer manager (the "Dealer Manager"), and Georgeson Shareholder
Communications, Inc., which is acting as the information agent (the "Information
Agent"), incurred in connection with the Offer. Following the consummation of
the Offer, Purchaser intends to effect the Merger described below.

THE OFFER, PRORATION PERIOD, AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00
MIDNIGHT, EASTERN TIME, ON MONDAY, JUNE 11, 2001, UNLESS THE OFFER IS EXTENDED.

THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, (1) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION DATE (AS DEFINED BELOW) AT
LEAST 16,730,502 SHARES (THE "MINIMUM CONDITION"); AND (2) THE EXPIRATION OR
TERMINATION OF THE WAITING PERIOD UNDER THE HART-SCOTT-RODINO ANTITRUST
IMPROVEMENTS ACT OF 1976, AS AMENDED, AND THE RULES AND REGULATIONS PROMULGATED
THEREUNDER. THE OFFER IS ALSO SUBJECT TO OTHER CONDITIONS SET FORTH IN THE OFFER
TO PURCHASE. THE OFFER IS NOT SUBJECT TO A FINANCING CONDITION. SEE SECTION 14
OF THE OFFER TO PURCHASE.

The Offer is being made pursuant to an Agreement and Plan of Merger, dated as of
May 7, 2001 (the "Merger Agreement"), by and among Williams, Purchaser and the
Company, pursuant to which, following the consummation of the Offer and in
accordance with the Delaware General Corporation Law, and subject to the
satisfaction or waiver of certain conditions, including approval of the Merger
by a majority of the outstanding Shares of the Company, either: (i) the Company
will be merged with and into Purchaser with Purchaser continuing as the
surviving corporation (the "Forward Merger"), with such Forward Merger to occur
in the event that Williams

   2
receives a written opinion from its tax counsel that the Offer and the Forward
Merger would be treated as a "reorganization" within the meaning of Section
368(a) of the Internal Revenue Code of 1986, as amended (the "Tax Opinion"); or
(ii) in the event that Williams is unable to obtain the Tax Opinion, Purchaser
(or another direct or indirect wholly owned subsidiary of Williams) may be
merged with and into the Company with the Company continuing as the surviving
corporation (the "Reverse Merger" and, together with the Forward Merger, the
"Merger"). The Offer is the first step of a two-step transaction, as
contemplated by the Merger Agreement, the purpose of which is to acquire control
of the Company.

At the effective time of the Merger (the "Effective Time") each Share issued and
outstanding immediately prior to the Effective Time (other than any Shares held
by the Company, Williams, Purchaser or any other subsidiary of Williams) will be
converted into the right to receive 1.767 shares of common stock, par value
$1.00, of Williams (together with the associated Williams Rights (as defined in
the Offer to Purchase), the "Williams Common Stock"). The Merger Agreement is
more fully described in the Offer to Purchase.

THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY APPROVED THE MERGER
AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY, INCLUDING THE OFFER AND THE
MERGER, HAS UNANIMOUSLY DETERMINED THAT THE OFFER AND THE MERGER ARE ADVISABLE
AND FAIR TO, AND IN THE BEST INTERESTS OF, THE COMPANY'S STOCKHOLDERS AND
UNANIMOUSLY RECOMMENDS THAT STOCKHOLDERS ACCEPT THE OFFER AND TENDER THEIR
SHARES PURSUANT TO THE OFFER AND APPROVE THE MERGER AT THE TIME OF THE COMPANY'S
STOCKHOLDER MEETING. IF THE OFFER AND THE MERGER ARE COMPLETED, PURCHASER WILL
PURCHASE 16,730,502 SHARES IN THE OFFER AT A PRICE OF $73.00 PER SHARE AND
HOLDERS OF THE REMAINING SHARES (INCLUDING ANY SHARES RETURNED TO TENDERING
STOCKHOLDERS AS A RESULT OF PRORATION) WILL RECEIVE 1.767 SHARES OF WILLIAMS
COMMON STOCK FOR EACH SHARE IN THE MERGER.

In the event that more than 16,730,502 Shares are validly tendered and not
withdrawn as of the Expiration Date of the Offer, Purchaser will accept for
payment and pay for only 16,730,502 Shares on a pro rata basis (with appropriate
adjustments to avoid purchase of fractional Shares) based on the number of
Shares properly tendered by each stockholder. As a result of proration, because
of the difficulty of determining the precise number of Shares properly tendered
and not withdrawn (due in part to the guaranteed delivery procedure described
under Section 3 of the Offer to Purchase), the Purchaser does not expect that it
will be able to announce the final results of such proration or pay for any
Shares until at least five New York Stock Exchange ("NYSE") trading days after
the Expiration Date. Preliminary results of proration will be announced by press
release as promptly as practicable after the Expiration Date. Stockholders may
obtain such preliminary information from the Information Agent and may be able
to obtain such information from their brokers. Tendering stockholders will not
receive payment for Shares accepted for payment pursuant to the Offer until the
final proration factor is known.

The term "Expiration Date" shall mean 12:00 Midnight, eastern time, on Monday,
June 11, 2001, unless and until Purchaser (in accordance with the terms of the
Merger Agreement) shall have extended the period of time during which the Offer
is open, in which event "Expiration Date" shall mean the latest time and date at
which the Offer, as so extended by Purchaser, shall expire. Subject to the
applicable rules and regulations of the Securities and Exchange Commission and
the provisions of the Merger Agreement, Purchaser expressly reserves the right,
in its sole discretion, at any time and from time to time, and regardless of
whether any of the events set forth in Section 14 of the Offer to Purchase shall
have occurred, (i) to extend the period of time during which the Offer is open
and thereby delay acceptance for payment of, and the payment for, any Shares, by
giving oral or written notice of such extension to the Depositary and (ii) to
amend the Offer in any respect by giving oral or written notice of such
amendment to the Depositary. Any such extension or amendment will be followed as
promptly as practicable by a public announcement thereof, such announcement in
the case of an extension, to be issued not later than 9:00 a.m., eastern time,
on the next business day after the previously scheduled Expiration Date. During
any such extension, all Shares previously tendered and not withdrawn will remain
subject to the Offer, subject to the right of a tendering stockholder to
withdraw such stockholder's Shares. Purchaser shall not provide for a subsequent
offering period in accordance with Rule 14d-11 under the Securities Exchange Act
of 1934, as amended (the "Exchange Act").

If Purchaser extends the time during which the Offer is open, or if Purchaser is
delayed in its acceptance for payment of or payment for Shares pursuant to the
Offer for any reason, then, without prejudice to Purchaser's rights under the
Offer, the Depositary may retain tendered Shares on Purchaser's behalf and those
Shares may not be withdrawn except to the extent tendering stockholders are
entitled to withdrawal rights as described in Section 4 of the Offer to
Purchase. However, Purchaser's ability to delay the payment for Shares that it
has accepted for payment is limited by Rule 14e-1(c) under the Exchange Act,
which requires that a bidder pay the consideration offered or return the
securities deposited by or on behalf of stockholders promptly after the
termination or withdrawal of such bidder's offer.

For purposes of the Offer, Purchaser will be deemed to have accepted for
payment, and thereby purchased, Shares validly tendered and not properly
withdrawn, if and when Purchaser gives oral or written notice to the Depositary
of Purchaser's acceptance for payment of such Shares pursuant to the Offer. Upon
the terms and subject to the conditions of the Offer, payment for Shares
accepted for payment pursuant to the Offer will be made by deposit of the
purchase price therefor with the Depositary, which will act as agent for
tendering stockholders for the purpose of receiving payments from Purchaser and
transmitting such payments to tendering stockholders whose Shares have been
accepted for payment. Under no circumstances will interest on the Offer Price
for Shares be paid, regardless of any delay in making such payment.

In all cases, payment for Shares accepted for payment pursuant to the Offer will
be made only after the timely receipt by the Depositary of (i)
   3
the certificates evidencing such Shares (the "Share Certificates") or
confirmation of a book-entry transfer of such Shares into the Depositary's
account at The Depository Trust Company (the "Book-Entry Transfer Facility")
pursuant to the procedures set forth in the Offer to Purchase, (ii) a Letter of
Transmittal, properly completed and duly executed, with any required signature
guarantees or, in the case of a book-entry transfer, an Agent's Message (as
defined in the Offer to Purchase) in lieu of the Letter of Transmittal, and
(iii) any other documents required by the Letter of Transmittal. Accordingly,
payment may be made to tendering stockholders at different times if delivery of
the Shares and other required documents occur at different times.

Tenders of Shares made pursuant to the Offer may be withdrawn at any time prior
to the Expiration Date. Thereafter, such tenders are irrevocable, except that
they may be withdrawn at any time after July 13, 2001, unless theretofore
accepted for payment as provided in the Offer to Purchase. For a withdrawal to
be effective, a written or facsimile transmission notice of withdrawal must be
timely received by the Depositary at one of its addresses set forth on the back
cover page of the Offer to Purchase. Any such notice of withdrawal must specify
the name and address of the person who tendered the Shares to be withdrawn, the
number of Shares to be withdrawn and the name of the registered holder of such
Shares, if different from that of the person who tendered the Shares. If Share
Certificates evidencing Shares to be withdrawn have been delivered or otherwise
identified to the Depositary, then, prior to the physical release of such Share
Certificates, the serial numbers shown on such Share Certificates must be
submitted to the Depositary and the signature(s) on the notice of withdrawal
must be guaranteed by an Eligible Institution (as defined in the Offer to
Purchase), unless such Shares have been tendered for the account of an Eligible
Institution. If Shares have been tendered pursuant to the procedures for
book-entry transfer as set forth in the Offer to Purchase, any notice of
withdrawal must also specify the name and number of the account at the
Book-Entry Transfer Facility to be credited with the withdrawn Shares and must
otherwise comply with the Book-Entry Transfer Facility's procedures. All
questions as to the form and validity (including time of receipt) of any notice
of withdrawal will be determined by Purchaser, in its sole discretion, whose
determination will be final and binding.

The receipt of cash in exchange for Shares pursuant to the Offer will be a
taxable transaction for U.S. federal income tax purposes and may also be a
taxable transaction under applicable state, local and other tax laws. In
general, a stockholder that receives cash in exchange for all of its Shares
pursuant to the Offer will recognize gain or loss for U.S. federal income tax
purposes equal to the difference between the amount of cash received and such
stockholder's tax basis in the Shares exchanged therefor. Provided that such
Shares constitute capital assets in the hands of the stockholder, such gain or
loss will be capital gain or loss, and will be long-term capital gain or loss if
the stockholder has held the Shares for more than one year at the time of sale.
A stockholder that exchanges all of its Shares for Williams Common Stock
pursuant to the Forward Merger will not recognize any gain or loss except with
respect to cash received in lieu of a fractional share of Williams Common Stock.
A stockholder that exchanges some of its Shares for cash pursuant to the Offer
and exchanges the rest of its Shares for Williams Common Stock pursuant to the
Forward Merger will recognize gain (but not loss) equal to the lesser of (i) the
amount of cash received pursuant to the Offer and (ii) an amount equal to the
excess, if any, of (a) the sum of the amount of cash received pursuant to the
Offer and the fair market value of the Williams Common Stock received pursuant
to the Forward Merger over (b) the stockholder's tax basis in its Shares. In the
event of a Reverse Merger, a stockholder would recognize all of its gain or loss
on the disposition of Shares pursuant to the Offer as well as the Reverse
Merger. All stockholders should consult with their own tax advisors as to the
particular tax consequences of the Offer and the Merger to them, including the
applicability and effect of any state, local and other tax laws and of changes
in such tax laws. For a more complete description of certain U.S. federal income
tax consequences of the Offer and the Merger, see Section 5 of the Offer to
Purchase.

The information required to be disclosed by paragraph (d)(1) of Rule 14d-6 of
the General Rules and Regulations under the Exchange Act is contained in the
Offer to Purchase and is incorporated herein by reference.

The Company has provided Purchaser with the Company's stockholder lists and
security position listings for the purpose of disseminating the Offer to holders
of Shares. The Offer to Purchase, the Letter of Transmittal and other relevant
documents will be mailed to record holders of Shares whose names appear on the
Company's stockholder list and will be furnished to brokers, dealers, commercial
banks, trust companies and similar persons whose names, or the names of whose
nominees, appear on the stockholder lists for subsequent transmittal to
beneficial owners of Shares.

THE OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN IMPORTANT
INFORMATION THAT SHOULD BE READ CAREFULLY BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.

Questions and requests for assistance and copies of the Offer to Purchase, the
Letter of Transmittal and all other tender offer materials may be directed to
the Information Agent or the Dealer Manager at their respective addresses and
telephone numbers set forth below and will be furnished promptly at Purchaser's
expense. Neither Williams nor Purchaser will pay any fees or commissions to any
broker or dealer or any other person (other than to the Dealer Manager, the
Depositary and the Information Agent) in connection with the solicitation of
tenders of Shares pursuant to the Offer.

The Information Agent for the Offer is:

Georgeson Shareholder Communications Inc.
17 State Street, 10th Floor
   4
New York, New York 10004
BANKS AND BROKERS CALL COLLECT: (212) 440-9800
ALL OTHERS CALL TOLL FREE: (800) 223-2064

The Dealer Manager for the Offer is:

Merrill Lynch & Co.
Four World Financial Center
New York, New York 10080
Call Collect: (212) 236-3790
 .
May 14, 2001

   1
                                                                Exhibit (a)(9)

                                                                 [WILLIAMS LOGO]

News Release

NYSE:WMB

================================================================================

Date:             May 14, 2001

                                                                                 
Contact:            Kelly Swan                         Rick Rodekohr                      Richard George
                    Williams (media relations)         Williams (investor relations)      Williams (investor relations)
                    (918) 573-6932                     (918) 573-2087                     (918) 573-3679
                    kelly.swan@williams.com            rick.rodekohr@williams.com         richard.george@williams.com

              WILLIAMS INITIATES TENDER OFFER FOR BARRETT RESOURCES
         Companies Moving Forward After Last Week's Definitive Agreement

         TULSA, Okla. - Williams (NYSE:WMB) announced today it has commenced a
cash tender offer at $73 per share for 16,730,502 shares of Barrett Resources
(NYSE:BRR) common stock. The offer is being made pursuant to the previously
announced definitive agreement to merge Barrett Resources with a unit of
Williams.
         The offer is scheduled to expire at midnight on June 11, 2001.
Following the tender offer, Williams intends to acquire the remaining equity
interest in Barrett Resources through a merger transaction in which each share
that was not purchased in the offer will be converted into 1.767 shares of
Williams common stock.
         The terms and conditions of the tender offer are fully set forth in
Williams' offer to purchase and the related letter of transmittal that are being
filed with the Securities and Exchange Commission today.
         The tender offer is subject to certain conditions, including obtaining
clearance of the transaction under federal antitrust laws and tenders of a
minimum of 16,730,502 shares of Barrett Resources common stock. If more than
16,730,502 shares are validly tendered into the offer and not withdrawn prior to
the expiration of the offer, Williams will accept for payment only 16,730,502
shares on a pro rata basis -- with appropriate adjustments to avoid purchase of
fractional shares -- based on the number of shares properly tendered by each
shareholder.
         The transaction would more than double Williams' natural gas reserves
while significantly enhancing the company's longer-term ability to profitably
grow its power business.

ADDITIONAL INFORMATION

         This news release is being filed pursuant to Rule 425 under the
Securities Act of 1933. It does not constitute an offer of sale of securities.
Shareholders of Barrett and other investors are urged to read the tender offer
materials, when available, and the proxy statement/prospectus that will be
included in the registration statement on Form S-4 to be filed by Williams in
connection with the second-step merger. These materials will

                                       1
   2
contain important information about Barrett, Williams, the merger, the people
soliciting proxies relating to the merger, their interests in the merger and
related matters.

         In addition to the tender offer materials and registration statement
and the joint proxy statement/prospectus to be filed in connection with the
merger, Williams and Barrett file annual, quarterly and special reports, proxy
statements and other information with the Securities and Exchange Commission.
You may read and copy any reports, statements or other information filed by
Barrett or Williams at the SEC Public Reference Rooms at 450 Fifth Street, N.W.,
Washington, D.C. 20549 or at any of the SEC's other public reference rooms in
New York and Chicago. Please call the SEC at (800) SEC-0330 for further
information on the public reference rooms. Williams' and Barrett's filings with
the SEC are also available to the public from commercial document-retrieval
services and at the web site maintained by the SEC at www.sec.gov. Free copies
of the tender offer materials and joint proxy statement/prospectus, when
available, and these other documents may also be obtained from Williams by
directing a request through the investor relations portion of Williams' website
at www.williams.com or by mail to Williams, One Williams Center, 50th Floor,
Tulsa, Okla., 74172, Attention: Investor Relations, Telephone: (800) 600-3782.

ABOUT WILLIAMS (NYSE: WMB)

Williams, through its subsidiaries, connects businesses to energy, delivering
innovative, reliable products and services. Williams information is available at
www.williams.com.

                                       ###

Portions of this document may constitute "forward-looking statements" as defined
by federal law. Although the company believes any such statements are based on
reasonable assumptions, there is no assurance that actual outcomes will not be
materially different. Any such statements are made in reliance on the "safe
harbor" protections provided under the Private Securities Reform Act of 1995.
Additional information about issues that could lead to material changes in
performance is contained in the company's annual reports filed with the
Securities and Exchange Commission.

                                       2
   1
                                                                Exhibit (d)(1)

                          AGREEMENT AND PLAN OF MERGER

                                      AMONG

                          THE WILLIAMS COMPANIES, INC.,

                           RESOURCES ACQUISITION CORP.

                                       AND

                          BARRETT RESOURCES CORPORATION

                             DATED AS OF MAY 7, 2001

   2

                                TABLE OF CONTENTS

                                                                                               
                                                 ARTICLE I
                                                 THE OFFER

Section 1.1  The Offer..................................................................................2
Section 1.2  Company Actions............................................................................4

                                                ARTICLE II
                                                THE MERGER

Section 2.1  The Merger.................................................................................5
Section 2.2  Closing....................................................................................5
Section 2.3  Effective Time.............................................................................5
Section 2.4  Effects of the Merger......................................................................6
Section 2.5  Certificate of Incorporation and Bylaws; Officers and Directors............................6
Section 2.6  Principal Offices of the Company...........................................................6

                                                ARTICLE III
                           EFFECT OF THE MERGER ON THE STOCK OF THE CONSTITUENT
                                  CORPORATIONS; EXCHANGE OF CERTIFICATES

Section 3.1  Effect on Stock............................................................................6
Section 3.2  Exchange of Certificates...................................................................7
Section 3.3  Tax Consequences...........................................................................9
Section 3.4  Adjustment of Exchange Ratio...............................................................9

                                                ARTICLE IV
                               REPRESENTATIONS AND WARRANTIES OF THE COMPANY

Section 4.1  Organization..............................................................................10
Section 4.2  Subsidiaries..............................................................................10
Section 4.3  Capital Structure.........................................................................10
Section 4.4  Authority.................................................................................11
Section 4.5  Consents and Approvals; No Violations.....................................................12
Section 4.6  SEC Documents and Other Reports...........................................................13
Section 4.7  Absence of Material Adverse Change........................................................13
Section 4.8  Information Supplied......................................................................14
Section 4.9  Compliance with Laws......................................................................14
Section 4.10  Tax Matters..............................................................................15
Section 4.11  Liabilities..............................................................................15
Section 4.12  Litigation...............................................................................15
Section 4.13  Benefit Plans............................................................................15
Section 4.14  State Takeover Statutes; Bylaws Provision; Rights Agreement..............................17
Section 4.15  Brokers..................................................................................17
Section 4.16  Voting Requirements......................................................................17
Section 4.17  Environmental Matters....................................................................17
Section 4.18  Contracts; Debt Instruments..............................................................19
Section 4.19  Title to Properties......................................................................19
Section 4.20  Intellectual Property....................................................................20

   3

                                                                                                   
Section 4.21  Condition of Assets......................................................................20
Section 4.22  Derivative Transactions..................................................................20

                                                 ARTICLE V
                             REPRESENTATIONS AND WARRANTIES OF PARENT AND SUB

Section 5.1  Organization..............................................................................21
Section 5.2  Capital Structure.........................................................................21
Section 5.3  Authority.................................................................................22
Section 5.4  Consents and Approvals; No Violations.....................................................22
Section 5.5  SEC Documents and Other Reports...........................................................23
Section 5.6  Absence of Material Adverse Change........................................................23
Section 5.7  Information Supplied......................................................................24
Section 5.8  Compliance with Laws......................................................................24
Section 5.9  Parent Shares.............................................................................24
Section 5.10  Reorganization...........................................................................24
Section 5.11  Liabilities..............................................................................25
Section 5.12  Interim Operations of Sub................................................................25
Section 5.13  Litigation...............................................................................25
Section 5.14  California Exposure......................................................................25
Section 5.15  Brokers..................................................................................25

                                                ARTICLE VI
                                 COVENANTS RELATING TO CONDUCT OF BUSINESS

Section 6.1  Conduct of Business Pending the Merger....................................................25
Section 6.2  No Solicitation; Acquisition Proposals....................................................28
Section 6.3  Third Party Standstill Agreements.........................................................30
Section 6.4  Disclosure of Certain Matters; Delivery of Certain Filings................................30
Section 6.5  Conduct of Business of Sub Pending the Merger.............................................31
Section 6.6  Modifications to Recommendations..........................................................31

                                                ARTICLE VII
                                           ADDITIONAL AGREEMENTS

Section 7.1  Employee Benefits.........................................................................32
Section 7.2  Options...................................................................................33
Section 7.3  Shareholder Approval; Preparation of Form S-4 and Proxy Statement/Prospectus..............35
Section 7.4  Access to Information.....................................................................36
Section 7.5  Fees and Expenses.........................................................................36
Section 7.6  Public Announcements......................................................................38
Section 7.7  Transfer Taxes............................................................................38
Section 7.8  State Takeover Laws.......................................................................38
Section 7.9  Indemnification; Directors and Officers Insurance.........................................38
Section 7.10  Board of Directors.......................................................................40
Section 7.11  HSR Act Filings; Reasonable Best Efforts.................................................40
Section 7.12  Stay Bonuses; Severance..................................................................42
Section 7.13  Section 16 Matters.......................................................................42
Section 7.14  Tax Treatment............................................................................42

                                       ii

   4

                                                                                                 
Section 7.15  Affiliate Letters........................................................................43
Section 7.16  Litigation...............................................................................43
Section 7.17  Rights Agreement.........................................................................43
Section 7.18  Bank Debt................................................................................43

                                               ARTICLE VIII
                                           CONDITIONS PRECEDENT

Section 8.1  Conditions to Each Party's Obligation to Effect the Merger................................44

                                                ARTICLE IX
                                         TERMINATION AND AMENDMENT

Section 9.1  Termination...............................................................................44
Section 9.2  Effect of Termination.....................................................................46
Section 9.3  Amendment.................................................................................46
Section 9.4  Extension; Waiver.........................................................................46

                                                 ARTICLE X
                                            GENERAL PROVISIONS

Section 10.1  Non-Survival of Representations and Warranties and Agreements............................46
Section 10.2  Notices..................................................................................46
Section 10.3  Interpretation; Definitions..............................................................47
Section 10.4  Counterparts.............................................................................54
Section 10.5  Entire Agreement; No Third-Party Beneficiaries...........................................54
Section 10.6  Governing Law............................................................................55
Section 10.7  Assignment...............................................................................55
Section 10.8  Severability.............................................................................55
Section 10.9  Enforcement of this Agreement............................................................55
Section 10.10  Obligations of Subsidiaries.............................................................55

                                      iii
   5

                          AGREEMENT AND PLAN OF MERGER

         AGREEMENT AND PLAN OF MERGER, dated as of May 7, 2001 (this
"Agreement") among The Williams Companies, Inc., a Delaware corporation
("Parent"), Resources Acquisition Corp., a Delaware corporation and a
wholly-owned subsidiary of Parent ("Sub"), and Barrett Resources Corporation, a
Delaware corporation (the "Company") (Sub and the Company being hereinafter
collectively referred to as the "Constituent Corporations"). Except as otherwise
set forth herein, capitalized (and certain other) terms used herein shall have
the meanings set forth in Section 10.3.

                                   WITNESSETH:

         WHEREAS, the Board of Directors of the Company has, in light of and
subject to the terms and conditions set forth herein, determined that a business
combination between Parent and the Company is fair to the Company's stockholders
and in the best interests of such stockholders;

         WHEREAS, it is intended that the acquisition be accomplished by Sub
commencing a cash tender offer for 16,730,502 outstanding shares of Common
Stock, par value $0.01 per share, of the Company ("Company Common Stock"),
together with the associated Company Rights, upon the terms and subject to the
conditions set forth in this Agreement (the shares of Company Common Stock
subject to the Offer, together with the associated Company Rights, are
hereinafter referred to as the "Shares") in an amount of $73.00 per Share (the
"Offer Consideration") to be followed by a merger of the Company with and into
Sub (the "Forward Merger");

         WHEREAS, subsequent to the purchase by Sub of Shares in the Offer, each
Share (other than Shares held directly or indirectly by Parent or the Company,
which Shares shall be cancelled) would be converted into the right to receive
1.767 (the "Exchange Ratio") duly authorized, validly issued, fully paid and
non-assessable shares of common stock, par value $1.00 (the "Parent Common
Stock" and, together with associated Parent Rights, the "Parent Shares") of
Parent (the "Merger Consideration");

         WHEREAS, if the Tax Opinion Standard (as defined herein) has not been
met, the parties desire to permit an alternate merger structure providing for
the merger of Sub (or other direct or indirect wholly-owned subsidiary of
Parent, as determined by Parent in its sole discretion) with and into the
Company (the "Reverse Merger"), and the surviving corporation shall thereby
become a direct or indirect wholly-owned subsidiary of Parent;

         WHEREAS, the Board of Directors of the Company has adopted resolutions
approving the Offer, this Agreement and the Merger (as defined herein),
determining that this Agreement is advisable and that the Offer and the Merger
are fair to, and in the best interests of, the Company's stockholders and
recommending that the Company's stockholders accept the Offer, tender their
Shares into the Offer and adopt this Agreement;

   6

         WHEREAS, the respective Boards of Directors of Parent, Sub and the
Company have each approved the Merger, upon the terms and subject to the
conditions set forth in this Agreement;

         WHEREAS, the respective Boards of Directors of Parent, Sub and the
Company have approved and adopted this Agreement and the transactions
contemplated hereby;

         WHEREAS, for Federal income tax purposes, it is intended that the Offer
and the Forward Merger shall be treated as an integrated transaction (together,
the "Transaction") and shall qualify as a "reorganization" within the meaning of
Section 368(a) of the Code and the United States Treasury Regulations; and

         WHEREAS, Parent, Sub and the Company each desires to make certain
representations, warranties, covenants and agreements in connection with the
Offer and the Merger and also to prescribe various conditions to the Offer and
the Merger.

         NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements herein contained, and intending to be legally bound
hereby, Parent, Sub and the Company hereby agree as follows:

                                    ARTICLE I
                                    THE OFFER

         Section 1.1 The Offer. (a) Provided that this Agreement shall not have
been terminated in accordance with Section 9.1 and subject to the provisions of
this Agreement, including the conditions to the Offer set forth in Exhibit A
hereto, as promptly as practicable after the date of the public announcement by
Parent and the Company of this Agreement, Sub shall, and Parent shall cause Sub
to, commence, within the meaning of Rule 14d-2 under the Exchange Act, the
Offer. The obligation of Sub to, and of Parent to cause Sub to, commence the
Offer and accept for payment, and pay for, any Shares tendered pursuant to the
Offer shall be subject only to the conditions set forth in Exhibit A (the "Offer
Conditions") (any one or more of which may be waived in whole or in part by Sub
in its sole discretion, provided that, without the prior written consent of the
Company, Sub shall not waive the Minimum Condition (as defined in Exhibit A)).
Sub expressly reserves the right to modify the terms of the Offer, except that,
without the prior written consent of the Company, Sub shall not (i) reduce the
number of Shares sought in the Offer, (ii) decrease the price per Share, (iii)
impose any conditions to the Offer in addition to the Offer Conditions or modify
the Offer Conditions in a manner adverse to the holders of Shares (other than to
waive any Offer Conditions to the extent permitted by this Agreement), (iv)
except as provided in (b) below, extend the Offer, (v) change the form of
consideration payable in the Offer (other than by adding consideration) or (vi)
make any other change or modification in any of the terms of the Offer in any
manner that is adverse to the holders of Shares.

                  (b) The Offer shall initially be scheduled to expire 20
business days following the commencement thereof. Parent and Sub agree that Sub
will not terminate the Offer between scheduled expiration dates (except in the
event that this Agreement is terminated pursuant to Section 9.1) and that, in
the event that Sub would otherwise be entitled to terminate the Offer at any
scheduled expiration date thereof due to the failure of one or more of the Offer
Conditions,

                                      -2-
   7

unless this Agreement shall have been terminated pursuant to Section 9.1, Sub
shall, and Parent shall cause Sub to, extend the Offer for such period or
periods as shall be determined by Sub until such date as the Offer Conditions
have been satisfied or such later date as required by applicable law; provided,
however, that nothing herein shall require Sub to extend the Offer beyond the
Outside Date. Notwithstanding the foregoing, Sub may, without the consent of the
Company, (i) extend the Offer, if at the scheduled or extended expiration date
of the Offer any of the Offer Conditions shall not be satisfied or waived, until
such time as such conditions are satisfied or waived and (ii) extend the Offer
for any period required by any rule, regulation, interpretation or position of
the SEC or the staff thereof applicable to the Offer or as might be required by
the NYSE. Sub shall not provide for a subsequent offering period in accordance
with Rule 14d-11 under the Exchange Act. Subject to the terms and conditions of
the Offer and this Agreement, Sub shall, and Parent shall cause Sub to, accept
and pay for 16,730,502 Shares validly tendered and not withdrawn pursuant to the
Offer that Sub is permitted to accept and exchange for under applicable law, as
soon as practicable after the expiration of the Offer, and in any event in
compliance with the obligations respecting prompt payment pursuant to Rule
14e-1(c) under the Exchange Act; provided, however, that no such payment shall
be made until after Parent and Sub shall have calculated how cash should be
prorated if more than 16,730,502 Shares are validly tendered and not withdrawn
pursuant to the Offer. If this Agreement is terminated by either Parent or Sub
or by the Company, Sub shall, and Parent shall cause Sub to, promptly terminate
the Offer.

                  (c) On the date of commencement of the Offer, Parent and Sub
shall file with the SEC a Tender Offer Statement on Schedule TO (together with
all supplements and amendments thereto, the "Schedule TO") with respect to the
Offer and a related letter of transmittal, and Parent and Sub shall cause the
Offer Documents to be disseminated to holders of Shares as and to the extent
required by applicable federal securities laws. Parent and Sub agree that they
shall cause the Schedule TO, the Offer to Purchase and all amendments or
supplements thereto (which together constitute the "Offer Documents") to comply
in all material respects with the Exchange Act and the rules and regulations
thereunder and other applicable laws. Parent, Sub and the Company each agrees
promptly to correct any information provided by it for use in the Offer
Documents if and to the extent that such information shall have become false or
misleading in any material respect, and Parent and Sub further agree to take all
steps necessary to cause the Offer Documents as so corrected to be filed with
the SEC and the other Offer Documents as so corrected to be disseminated to
holders of Shares, in each case as and to the extent required by applicable
federal securities laws. The Company and its counsel shall be given reasonable
opportunity to review and comment upon the Offer Documents prior to their filing
with the SEC or dissemination to the Company's stockholders. Parent and Sub
agree to provide the Company and its counsel any comments Parent, Sub or their
counsel may receive from the SEC or its staff with respect to the Offer
Documents promptly after the receipt of such comments and to cooperate with the
Company and its counsel in responding to such comments.

                  (d) Parent shall provide or cause to be provided to Sub on a
timely basis all funds necessary to accept for payment, and pay for, any Shares
accepted for payment that are validly tendered and not withdrawn pursuant to the
Offer and that Sub is permitted to accept for payment pursuant to the terms and
conditions of the Offer and under applicable law.

                                      -3-
   8

         Section 1.2 Company Actions. (a) The Company hereby approves of and
consents to the Offer and represents and warrants that the Board of Directors of
the Company, at a meeting duly called and held, duly adopted resolutions by
unanimous vote (i) determining that this Agreement and the transactions
contemplated hereby, including the Offer and the Merger, are advisable and are
fair to and in the best interest of the Company's stockholders, (ii) approving
this Agreement and the transactions contemplated hereby, including the Offer and
the Merger, which approval constitutes approval under Section 203 of the DGCL
such that the Offer, the Merger and this Agreement and the other transactions
contemplated hereby are not and shall not be subject to any restriction of
Section 203 of the DGCL, (iii) waiving the application of Article IV of the
Company's bylaws with respect to this Agreement, the Offer and the Merger
pursuant to Section 7 thereof and (iv) resolving to recommend acceptance of the
Offer and to recommend that stockholders of the Company tender their Shares
pursuant to the Offer and to recommend approval and adoption of this Agreement
and the Merger by the Company's stockholders at the Company Stockholders Meeting
(as defined herein) (the recommendations referred to in this clause (iv) are
collectively referred to in this Agreement as the "Recommendations"). The
Company represents and warrants that its Board of Directors has received the
opinion, each dated May 7, 2001, of each of Goldman, Sachs & Co. ("Goldman
Sachs") and Petrie Parkman & Co., Inc. ("Petrie Parkman") that, as of such date
and on the basis of and subject to the matters described therein, the Offer
Consideration and the Merger Consideration, taken together, was fair to the
Company's stockholders (other than Parent and the Company) from a financial
point of view.

                  (b) On the date the Offer Documents are filed with the SEC,
the Company shall file with the SEC a Solicitation/Recommendation Statement on
Schedule 14D-9 with respect to the Offer (such Schedule 14D-9, as amended from
time to time, the "Schedule 14D-9") containing the Recommendations (subject to
the right of the Board of Directors of the Company to make a Subsequent
Determination in accordance with Section 6.6 and shall cause the Schedule 14D-9
to be disseminated to the Company's stockholders as and to the extent required
by applicable federal securities laws. Each of the Company, Parent and Sub
agrees promptly to correct any information provided by it for use in the
Schedule 14D-9 if and to the extent that such information shall have become
false or misleading in any material respect, and the Company further agrees to
take all steps necessary to amend or supplement the Schedule 14D-9 and to cause
the Schedule 14D-9 as so amended or supplemented to be filed with the SEC and
disseminated to the Company's stockholders, in each case as and to the extent
required by applicable federal securities laws. Parent and its counsel shall be
given reasonable opportunity to review and comment upon the Schedule 14D-9 prior
to its filing with the SEC or dissemination to the Company's stockholders. The
Company agrees to provide Parent and its counsel any comments the Company or its
counsel may receive from the SEC or its staff with respect to the Schedule 14D-9
promptly after the receipt of such comments and to cooperate with Parent, Sub
and their counsel in responding to such comments.

                  (c) In connection with the Offer and the Merger, the Company
shall cause its transfer agent to furnish Sub promptly with mailing labels
containing the names and addresses of the record holders of Shares as of a
recent date and of those persons becoming record holders subsequent to such
date, together with copies of all lists of stockholders, security position
listings and computer files and all other information in the Company's
possession or control regarding the beneficial owners of Shares and any
securities convertible into Shares, and shall furnish to

                                      -4-
   9

Sub such information and assistance (including updated lists of stockholders,
security position listings and computer files) as Parent or Sub may reasonably
request in communicating the Offer to the Company's stockholders. Subject to the
requirements of applicable law, and except for such steps as are necessary to
disseminate the Offer Documents and any other documents necessary to consummate
the Merger, Parent and Sub and their affiliates, associates and agents shall
hold in confidence the information contained in any such labels, listings and
files, will use such information only in connection with the Offer and the
Merger and, if this Agreement shall be terminated, will promptly, upon request,
deliver, and will use reasonable efforts to cause their affiliates, associates
and agents to deliver, to the Company all copies of such information then in
their possession or control.

                                   ARTICLE II
                                   THE MERGER

         Section 2.1 The Merger. Upon the terms and subject to the conditions
hereof, and in accordance with the DGCL, the Forward Merger shall be effected
and the Company shall be merged with and into Sub at the Effective Time;
provided, however, that if Parent does not obtain a written opinion of Tax
Counsel (as defined herein) that satisfies the Tax Opinion Standard (as defined
herein), then in Parent's reasonable discretion the Reverse Merger may be
effected, and the surviving corporation shall thereby become a direct or
indirect wholly-owned subsidiary of Parent. Following the Effective Time, if the
Forward Merger is effected, then the separate existence of the Company shall
cease and Sub shall continue as the surviving corporation or, if the Reverse
Merger is effected, then the separate existence of Sub shall cease and the
Company shall continue as the surviving corporation. The surviving corporation
of the Forward Merger or the Reverse Merger, as the case may be, shall be herein
referred as the "Surviving Corporation" and the Forward Merger and Reverse
Merger shall collectively be referred to as the "Merger." The Surviving
Corporation shall succeed to and assume all the rights and obligations of Sub
and the Company in accordance with the DGCL.

         Section 2.2 Closing. The closing of the Merger will take place at 10:00
a.m. on a date mutually agreed to by Parent and the Company, which shall be no
later than the second business day after satisfaction or waiver of the
conditions set forth in Article VIII (the "Closing Date"), at the offices of
Sidley Austin Brown & Wood, Bank One Plaza, 10 South Dearborn Street, Chicago,
Illinois 60603, unless another date, time or place is agreed to in writing by
the parties hereto.

         Section 2.3 Effective Time. The Merger shall become effective when a
Certificate of Merger (the "Certificate of Merger"), executed in accordance with
the relevant provisions of the DGCL, is duly filed with the Secretary of State
of the State of Delaware, or at such other time as Sub and the Company shall
agree should be specified in the Certificate of Merger. When used in this
Agreement, the term "Effective Time" shall mean the later of the date and time
at which the Certificate of Merger is duly filed with the Secretary of State of
the State of Delaware or such later time established by the Certificate of
Merger. The filing of the Certificate of Merger shall be made as soon as
practicable after the satisfaction or waiver of the conditions to the Merger set
forth in Article VIII.

                                      -5-
   10

         Section 2.4 Effects of the Merger. The Merger shall have the effects
set forth in the DGCL.

         Section 2.5 Certificate of Incorporation and Bylaws; Officers and
Directors. (a) At the Effective Time, the Certificate of Incorporation of Sub,
as in effect immediately prior to the Effective Time, shall be the Restated
Certificate of Incorporation of the Surviving Corporation until thereafter
changed or amended as provided therein or by applicable law; provided, however,
that the Certificate of Incorporation shall provide that the Surviving
Corporation shall initially be named "Barrett Resources Corporation" and shall
contain indemnification provisions consistent with the obligations set forth in
Section 7.9(a).

                  (b) The Bylaws of Sub, as in effect immediately prior to the
Effective Time, shall be the Bylaws of the Surviving Corporation until
thereafter changed or amended as provided by the Certificate of Incorporation of
the Surviving Corporation or by applicable law; provided that the Bylaws of the
Surviving Corporation shall contain indemnification provisions consistent with
the obligations set forth in Section 7.9(a).

                  (c) The directors of Sub immediately prior to the Effective
Time shall be the directors of the Surviving Corporation, until the earlier of
their resignation or removal or until their respective successors are duly
elected and qualified, as the case may be.

                  (d) The officers of the Company immediately prior to the
Effective Time shall be the officers of the Surviving Corporation until the
earlier of their resignation or removal or until their respective successors are
duly elected and qualified, as the case may be.

         Section 2.6 Principal Offices of the Company. Parent currently
anticipates that the Company's current principal offices in Denver, Colorado
will serve as the Rocky Mountain principal offices for Parent's oil and gas
exploration operations after the consummation of the Merger.

                                  ARTICLE III
                    EFFECT OF THE MERGER ON THE STOCK OF THE
               CONSTITUENT CORPORATIONS; EXCHANGE OF CERTIFICATES

         Section 3.1 Effect on Stock. As of the Effective Time, by virtue of the
Merger and without any action on the part of any of Sub, the Company or the
holders of any securities of the Constituent Corporations:

                  (a) Capital Stock of Sub. In the event of a Forward Merger,
each issued and outstanding share of capital stock of Sub shall remain as one
validly issued, fully paid and nonassessable share of Common Stock, no par
value, of the Surviving Corporation. Notwithstanding the foregoing, in the event
of a Reverse Merger, then each issued and outstanding share of capital stock of
Sub shall be converted into and become one validly issued, fully paid and
non-assessable share of Common Stock of the Surviving Corporation.

                  (b) Treasury Stock and Parent Owned Stock. Each Share that is
owned by the Company, Parent, Sub (except for Shares that are owned by Sub, in
the event of a Reverse

                                      -6-
   11

Merger) or any other Subsidiary of Parent shall automatically be cancelled and
retired and shall cease to exist, and no consideration shall be delivered in
exchange therefor.

                  (c) Conversion of Shares. Each Share issued and outstanding
(other than Shares to be cancelled in accordance with Section 3.1(b) and other
than Shares owned by Sub in the event of a Reverse Merger), shall be converted
into the right to receive a number of duly authorized, validly issued, fully
paid and non-assessable Parent Shares equal to the Exchange Ratio (the "Merger
Consideration"). As of the Effective Time, all such Shares, when so converted,
shall no longer be outstanding and shall automatically be cancelled and retired,
and each holder of a certificate representing any such Shares shall cease to
have any rights with respect thereto, except the right to receive any dividends
or distributions in accordance with Section 3.2(c), certificates representing
the Parent Shares into which such Shares are converted and any cash, without
interest, in lieu of fractional shares to be issued or paid in consideration
therefor upon the surrender of such certificate in accordance with Section
3.2(d).

                  (d) Notwithstanding anything expressed or implied to the
contrary in this Agreement, appropriate modifications shall be made to the
provisions of this Agreement (including, without limitation, this Section 3.1)
in the event of a Reverse Merger involving a direct or indirect wholly-owned
subsidiary of Parent (other than Sub).

         Section 3.2 Exchange of Certificates. (a) At the Effective Time, Parent
shall deposit, or shall cause to be deposited, with a banking or other financial
institution mutually acceptable to Parent and the Company (the "Exchange
Agent"), for the benefit of the holders of Shares, for exchange in accordance
with this Article III, certificates representing the Parent Shares to be issued
in connection with the Merger and cash in lieu of fractional shares (such cash
and certificates for Parent Shares, together with any dividends or distributions
with respect thereto (relating to record dates for such dividends or
distributions after the Effective Time), being hereinafter referred to as the
"Exchange Fund") to be issued pursuant to Section 3.1 and paid pursuant to this
Section 3.2 in exchange for outstanding Shares.

                  (b) Exchange Procedure. As soon as practicable after the
Effective Time, the Surviving Corporation shall cause the Exchange Agent to mail
to each holder of record of a certificate or certificates that immediately prior
to the Effective Time represented Shares (the "Certificates"), (i) a letter of
transmittal (which shall specify that delivery shall be effected, and risk of
loss and title to the Certificates shall pass, only upon delivery of the
Certificates to the Exchange Agent and shall be in a form and have such other
provisions as Parent may reasonably specify) and (ii) instructions for use in
effecting the surrender of the Certificates in exchange for the consideration
contemplated by Section 3.1 and this Section 3.2, including cash in lieu of
fractional shares. Upon surrender of a Certificate for cancellation to the
Exchange Agent, together with such letter of transmittal, duly executed, and
such other documents as may reasonably be required by the Exchange Agent, the
holder of such Certificate shall be entitled to receive in exchange therefor (x)
a certificate representing that number of whole Parent Shares and (y) a check
representing the amount of cash in lieu of fractional shares, if any, and unpaid
dividends and distributions with respect to the Parent Shares as provided for in
Section 3.2(c), if any, that such holder has the right to receive in respect of
the Certificate surrendered pursuant to the provisions of this Article III,
after giving effect to any required withholding tax, and the Shares represented
by the Certificate so surrendered shall forthwith be canceled. No interest will

                                      -7-
   12

be paid or accrued on the cash payable to holders of Shares. In the event of a
transfer of ownership of Shares that is not registered in the transfer records
of the Company, a certificate representing the proper number of Parent Shares,
together with a check for the cash to be paid pursuant to this Section 3.2 may
be issued to such a transferee if such Certificate shall be properly endorsed or
otherwise be in proper form for transfer and the transferee shall pay any
transfer or other taxes required by reason of the payment to a person other than
the registered holder of such Certificate or establish to the satisfaction of
the Surviving Corporation that such tax has been paid or is not applicable.
Parent or the Exchange Agent shall be entitled to deduct and withhold from the
consideration otherwise payable pursuant to this Agreement to any holder of
Shares such amounts as Parent or the Exchange Agent is required to deduct and
withhold with respect to the making of such payment under the Code or under any
provision of state, local or foreign tax law. To the extent that amounts are so
withheld by Parent or the Exchange Agent, such withheld amounts shall be treated
for all purposes of this Agreement as having been paid to the holder of the
Shares in respect of which such deduction and withholding was made by Parent or
the Exchange Agent.

                  (c) Dividends. Notwithstanding any other provisions of this
Agreement, no dividends or other distributions declared with a record date after
the Effective Time on Parent Shares shall be paid with respect to any Shares
represented by a Certificate until such Certificate is surrendered for exchange
as provided herein. Following surrender of any such Certificate, there shall be
paid to the holder of the certificates representing whole Parent Shares issued
in exchange therefor, without interest, (i) at the time of such surrender, the
amount of dividends or other distributions with a record date after the
Effective Time theretofore payable with respect to such whole Parent Shares and
not paid, less the amount of any withholding taxes which may be required
thereon, and (ii) at the appropriate payment date, the amount of dividends or
other distributions with a record date after the Effective Time but prior to
surrender and a payment date subsequent to surrender payable with respect to
such whole Parent Shares, less the amount of any withholding taxes which may be
required thereon. Parent will provide the Exchange Agent with the cash necessary
to make the payments contemplated by this Section 3.2(c).

                  (d) No Fractional Securities. No fractional Parent Shares
shall be issued pursuant hereto. In lieu of the issuance of any fractional share
of Parent Shares, cash adjustments will be paid to holders in respect of any
fractional share of Parent Shares that would otherwise be issuable, and the
amount of such cash adjustment shall be equal to the product obtained by
multiplying such stockholder's fractional share of Parent Shares that would
otherwise be issuable to such holder by the closing price per share of Parent
Shares on the NYSE on the Closing Date as reported by The Wall Street Journal
(or, if not reported thereby, any other authoritative source).

                  (e) No Further Ownership Rights in Shares. All Parent Shares
issued upon the surrender for exchange of Certificates in accordance with the
terms of this Article III (including any cash paid pursuant to this Section 3.2)
shall be deemed to have been issued in full satisfaction of all rights
pertaining to the Shares theretofore represented by such Certificates. At the
Effective Time, the stock transfer books of the Company shall be closed, and
there shall be no further registration of transfers on the stock transfer books
of the Surviving Corporation of the Shares that were outstanding immediately
prior to the Effective Time. If, after the Effective

                                      -8-
   13

Time, Certificates are presented to the Surviving Corporation or the Exchange
Agent for any reason, they shall be cancelled and exchanged as provided in this
Article III.

                  (f) Termination of Exchange Fund. Any portion of the Exchange
Fund (including the proceeds of any investments thereof and any Parent Shares)
which remains undistributed to the holders of Shares for twelve months after the
Effective Time shall be delivered to Parent, upon demand, and any holders of
Shares who have not theretofore complied with this Article III and the
instructions set forth in the letter of transmittal mailed to such holders after
the Effective Time shall thereafter look only to the Surviving Corporation
(subject to abandoned property, escheat or other similar laws) for payment of
their Parent Shares, cash and unpaid dividends and distributions on Parent
Shares deliverable in respect of each Share such stockholder holds as determined
pursuant to this Agreement, in each case, without any interest thereon.

                  (g) No Liability. None of Parent, Sub, the Company or the
Exchange Agent shall be liable to any person in respect of any amount properly
delivered to a public official pursuant to any applicable abandoned property,
escheat or similar law.

                  (h) Lost Certificates. If any Certificate shall have been
lost, stolen or destroyed, upon the making of an affidavit of that fact by the
Person claiming such Certificate to be lost, stolen or destroyed and, if
required by Parent, the posting by such Person of a bond in such reasonable
amount as Parent may direct as indemnity against any claim that may be made
against it with respect to such Certificate, the Exchange Agent shall issue in
exchange for such lost, stolen or destroyed Certificate the applicable Merger
Consideration with respect thereto and, if applicable, any unpaid dividends and
distributions on shares of Parent Shares deliverable in respect thereof and any
cash in lieu of fractional shares, in each case pursuant to this Agreement.

         Section 3.3 Tax Consequences. It is intended by the parties hereto that
the Transaction shall constitute a "reorganization" within the meaning of
Section 368(a) of the Code and the United States Treasury Regulations
thereunder.

         Section 3.4 Adjustment of Exchange Ratio. In the event that Parent
changes or establishes a record date for changing the number of Parent Shares
issued and outstanding as a result of a stock split, stock dividend,
recapitalization, subdivision, reclassification, combination or similar
transaction with respect to the outstanding Parent Shares and the record date
therefor shall be prior to the Effective Time, the Exchange Ratio applicable to
the Merger and any other calculations based on or relating to Parent Shares
shall be appropriately adjusted to reflect such stock split, stock dividend,
recapitalization, subdivision, reclassification, combination or similar
transaction.

                                   ARTICLE IV
                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         Each exception set forth in the Company Letter (as defined herein) to
the representations and warranties in this Article IV and each other response to
this Agreement set forth in the Company Letter is identified by reference to, or
has been grouped under a heading referring to, a specific individual Section of
this Agreement and relates only to such Section, except to the extent that one
section of the Company Letter specifically refers to or reasonably relates to

                                      -9-
   14

another section thereof. Except as set forth in the Company Letter, the Company
represents and warrants to Parent and Sub as follows:

         Section 4.1 Organization. The Company and each of its Significant
Subsidiaries is duly organized, validly existing and in good standing under the
laws of the jurisdiction of its organization and has requisite power and
authority to carry on its business as now being conducted, except where the
failure to be so organized, existing and in good standing or to have such power
and authority would not reasonably be expected to have a Material Adverse Effect
on the Company. The Company and each of its Significant Subsidiaries is duly
qualified or licensed to do business and in good standing in each jurisdiction
in which the nature of its business or the ownership or leasing of its
properties makes such qualification or licensing necessary, except in such
jurisdictions where the failure to be so duly qualified or licensed and in good
standing (individually or in the aggregate) would not reasonably be expected to
have a Material Adverse Effect on the Company or prevent or materially delay the
consummation of the Offer and/or the Merger. The Company has made available to
Parent complete and correct copies of its certificate of incorporation and
bylaws and the certificate of incorporation and bylaws (or similar
organizational documents) of each of its Significant Subsidiaries, in each case
as amended through the Closing Date.

         Section 4.2 Subsidiaries. Item 4.2 of the disclosure letter delivered
by the Company to Parent and Sub prior to the execution of this Agreement (the
"Company Letter") lists each Subsidiary of the Company and its respective
jurisdiction of incorporation and indicates whether such Subsidiary is a
Significant Subsidiary. All of the outstanding shares of capital stock or
ownership interest of each such Subsidiary of the Company that is a corporation
have been validly issued and are fully paid and nonassessable. Except as set
forth in Item 4.2 of the Company Letter, all of the outstanding shares of
capital stock or ownership interest of each Subsidiary of the Company are owned
by the Company, by one or more Subsidiaries of the Company or by the Company and
one or more Subsidiaries of the Company, free and clear of all Liens (including
any restriction on the right to vote, sell or otherwise dispose of such capital
stock). Except as set forth in Item 4.2 of the Company Letter and except for the
capital stock of its Subsidiaries, the Company does not own, directly or
indirectly, any capital stock or other ownership interest in any Person.

         Section 4.3 Capital Structure. (a) The authorized capital stock of the
Company consists of 45,000,000 shares of Company Common Stock and 1,000,000
Preferred Shares, par value $.001 per share (the "Company Preferred Stock") of
which 75,000 shares have been designated as Series A Junior Participating
Preferred Stock (the "Company Series A Preferred Shares"). At the close of
business on May 3, 2001, (i) 33,461,004 shares of Company Common Stock were
issued and outstanding, all of which were validly issued, fully paid and
nonassessable and free of preemptive rights, (ii) 4,999 shares of Company Common
Stock were held by the Company in its treasury, (iii) 2,302,073 shares of
Company Common Stock were reserved for issuance pursuant to outstanding options
to purchase Company Common Stock (the "Company Stock Options") granted under the
Company's 2000 Stock Option Plan, 1999 Stock Option Plan, 1997 Stock Option
Plan, 1994 Stock Option Plan, Plains Petroleum Company 1992 Stock Option Plan,
1990 Barrett Resources Corporation Nondiscretionary Stock Option Plan, Plains
Petroleum Company 1989 Stock Option Plan and Plains Petroleum Company 1985 Stock
Option Plan for Non-Employee Directors (together, and each as amended, the
"Company Stock Plans") and (iv)

                                      -10-
   15

no shares of Company Preferred Stock were issued and outstanding. As of the date
of this Agreement, except for (i) the rights to purchase Company Series A
Preferred Shares (the "Company Rights") issued pursuant to the Rights Agreement
dated as of August 5, 1997, as amended pursuant to the Amendment to Rights
Agreement dated as of February 25, 1999 and May 7, 2001 (as amended, the
"Company Rights Agreement") between the Company and BankBoston, N.A., as Rights
Agent (the "Company Rights Agent") or (ii) as set forth above, no Shares were
issued, reserved for issuance or outstanding and there are not any phantom stock
or other contractual rights the value of which is determined in whole or in part
by the value of any capital stock of the Company ("Stock Equivalents"). There
are no outstanding stock appreciation rights with respect to the capital stock
of the Company. Each outstanding Share is, and each Share which may be issued
pursuant to the Company Stock Plans will be, when issued, duly authorized,
validly issued, fully paid and nonassessable and not subject to preemptive
rights. There are no outstanding bonds, debentures, notes or other indebtedness
of the Company having the right to vote (or convertible into, or exchangeable
for, securities having the right to vote) on any matter on which the Company's
stockholders may vote. Except as set forth above or in Item 4.3 of the Company
Letter, as of the date of this Agreement, there are no securities, options,
warrants, calls, rights, commitments, agreements, arrangements or undertakings
of any kind to which the Company or any of its Significant Subsidiaries is a
party or by which any of them is bound obligating the Company or any of its
Significant Subsidiaries to issue, deliver or sell or create, or cause to be
issued, delivered or sold or created, additional shares of capital stock or
other voting securities or Stock Equivalents of the Company or of any of its
Significant Subsidiaries or obligating the Company or any of its Significant
Subsidiaries to issue, grant, extend or enter into any such security, option,
warrant, call, right, commitment, agreement, arrangement or undertaking. There
are no outstanding rights, commitments, agreements, or undertakings of any kind
obligating the Company or any of its Subsidiaries to repurchase, redeem or
otherwise acquire any shares of capital stock or other voting securities of the
Company or any of its Subsidiaries or any securities of the type described in
the two immediately preceding sentences.

                  (b) The Company has delivered or made available to Parent
complete and correct copies of the Company Stock Plans and all forms of Company
Stock Options. Item 4.3 of the Company Letter sets forth a complete and accurate
list of all Company Stock Options outstanding as of the date of this Agreement
and the exercise price of each outstanding Company Stock Option.

         Section 4.4 Authority. The Company has the requisite corporate power
and authority to execute and deliver this Agreement and, subject to adoption by
the Company's stockholders of this Agreement with respect to the Merger (if
required by applicable law), to consummate the transactions contemplated hereby.
The execution, delivery and performance of this Agreement by the Company and the
consummation by the Company of the Merger and of the other transactions
contemplated hereby have been duly authorized by all necessary corporate action
on the part of the Company, subject to adoption by the Company's stockholders of
this Agreement (if required by applicable law). This Agreement has been duly
executed and delivered by the Company and (assuming the valid authorization,
execution and delivery of this Agreement by Parent and Sub) constitutes the
valid and binding obligation of the Company, enforceable against the Company in
accordance with its terms, except that such enforceability (i) may be limited by

                                      -11-
   16

bankruptcy, insolvency, moratorium or other similar laws affecting or relating
to the enforcement of creditors' rights generally and (ii) is subject to general
principles of equity.

         Section 4.5 Consents and Approvals; No Violations. Except as set forth
in Item 4.5 of the Company Letter, (a) The execution and delivery of this
Agreement do not, and the consummation of the transactions contemplated by this
Agreement and compliance with the provisions of this Agreement will not,
conflict with, or result in any violation of, or default (with or without notice
or lapse of time, or both) under, or give rise to a right of termination,
cancellation or acceleration of any obligation or to loss of a material benefit
under, or result in the creation of any Lien upon any of the properties or
assets of the Company or any of its Subsidiaries under, (i) the certificate of
incorporation or bylaws of the Company or the comparable charter or
organizational documents of any of its Subsidiaries, (ii) any loan or credit
agreement, note, bond, mortgage, indenture, lease or other agreement,
instrument, permit, concession, franchise or license applicable to the Company
or any of its Subsidiaries or their respective properties or assets or (iii)
subject to the governmental filings and other matters referred to in clause (b)
of this Section 4.5, any judgment, order, decree, statute, law, ordinance, rule
or regulation applicable to the Company or any of its Subsidiaries or their
respective properties or assets, other than, in the case of clauses (ii) and
(iii), any such conflicts, violations, defaults, rights, losses or Liens that
individually or in the aggregate could not reasonably be expected to (x) have a
Material Adverse Effect on the Company, (y) materially impair the Company's
ability to perform its obligations under this Agreement or (z) prevent or
materially delay the consummation of the transactions contemplated by this
Agreement.

                  (b) No consent by a Governmental Entity is required by or with
respect to the Company or any of its Subsidiaries in connection with the
execution and delivery of this Agreement by the Company or the consummation by
the Company of the transactions contemplated by this Agreement, except for (i)
the filing of a premerger notification and report form by the Company under the
HSR Act and any applicable filings under similar foreign antitrust or
competition laws and regulations, (ii) the filing with the SEC of (A) the
Schedule 14D-9, (B) a proxy statement relating to the Company Stockholders
Meeting (as amended or supplemented from time to time, the "Proxy Statement"),
and (C) such reports, schedules, forms and statements under the Exchange Act and
the Securities Act, as may be required in connection with this Agreement and the
transactions contemplated hereby, (iii) such filings as may be required under
state securities or "blue sky" laws, (iv) the filing of the Certificate of
Merger with the Delaware Secretary of State and appropriate documents with the
relevant authorities of other states in which the Company is qualified to do
business, and (v) such other consents, approvals, orders, authorizations,
registrations, declarations and filings the failure of which to be made or
obtained individually or in the aggregate could not reasonably be expected to
(x) have a Material Adverse Effect on the Company, (y) impair the Company's
ability to perform its obligations under this Agreement or (z) prevent or
materially delay the consummation of the transactions contemplated by this
Agreement.

                  (c) Except as otherwise disclosed in Item 4.5(c) of the
Company Letter, neither the Company nor any of its Subsidiaries is a party to or
subject to any material agreement, contract, policy, license, Permit, document,
instrument, arrangement or commitment that provides for an express
non-competition covenant with any Person or in any geographic area and

                                      -12-
   17

which limits in any material respect the ability of the Company to compete in
its current business line.

         Section 4.6 SEC Documents and Other Reports. The Company has filed with
the SEC all required reports, schedules, forms, statements and other documents
required to be filed by it since April 1, 1998 under the Securities Act or the
Exchange Act (the "Company SEC Documents"). As of their respective filing dates,
the Company SEC Documents complied in all material respects with the
requirements of the Securities Act or the Exchange Act, as the case may be, each
as in effect on the date so filed, and at the time filed with the SEC none of
the Company SEC Documents contained any untrue statement of a material fact or
omitted to state a material fact required to be stated therein or necessary to
make the statements therein, in light of the circumstances under which they were
made, not misleading. The financial statements of the Company included in the
Company SEC Documents comply as of their respective dates in all material
respects with the then applicable accounting requirements and the published
rules and regulations of the SEC with respect thereto, have been prepared in
accordance with GAAP (except in the case of the unaudited statements, as
permitted by Form 10-Q under the Exchange Act) applied on a consistent basis
during the periods involved (except as may be indicated therein or in the notes
thereto) and fairly present in all material respects the consolidated financial
position of the Company and its consolidated Subsidiaries as at the dates
thereof and the consolidated results of their operations and their consolidated
cash flows for the periods then ended (subject, in the case of unaudited
statements, to normal year-end audit adjustments and to any other adjustments
described therein not material in amount).

         Section 4.7 Absence of Material Adverse Change. Except as disclosed in
Item 4.7 of the Company Letter or in the documents filed by the Company with the
SEC and publicly available prior to the date of this Agreement (the "Company
Filed SEC Documents"), since December 31, 2000 the Company and its Subsidiaries
have conducted their respective businesses in all material respects only in the
ordinary course consistent with past practice and there has not been (i) any
Material Adverse Change with respect to the Company, (ii) any declaration,
setting aside or payment of any dividend or other distribution (whether in cash,
stock or property) with respect to its capital stock or any redemption, purchase
or other acquisition of any of its capital stock, (iii) any split, combination
or reclassification of any of its capital stock or any issuance or the
authorization of any issuance of any other securities in respect of, in lieu of
or in substitution for shares of its capital stock, (iv) any change in
accounting methods, principles or practices by the Company, except insofar as
may have been required by a change in GAAP, (v) except in the ordinary course of
business or as required under plans or agreements in effect prior to January 1,
2001, (A) any granting by the Company or any of its Subsidiaries to any current
or former director, officer or employee of the Company or any of its
Subsidiaries of any increase in compensation, (B) any granting by the Company or
any of its Subsidiaries to any such director, officer or employee of any
increase in severance or termination pay (including the acceleration in the
exercisability of options to purchase, the re-pricing of options to purchase, or
in the vesting of, Company Common Stock (or other property)), in excess of 10%
of the potential amount payable under plans in effect as of December 31, 2000,
or (C) any entry by the Company or any of its Subsidiaries into any material
employment, deferred compensation, severance or termination agreement with any
such current or former director, officer, or employee; (vi) any damage,
destruction or loss, whether or not covered by insurance, that has had or could
reasonably be expected to have a Material Adverse Effect on the Company, (vii)
any amendment

                                      -13-
   18

of any material term of any outstanding security of the Company or any of its
Subsidiaries, (viii) any incurrence, assumption or guarantee by the Company or
any of its Subsidiaries of any indebtedness for borrowed money other than in the
ordinary course of business consistent with past practice in the amount of more
than $10 million in the aggregate through the date of this Agreement, (ix) any
creation or assumption by the Company or any of its Subsidiaries of any material
Lien on any asset other than in the ordinary course of business consistent with
past practice, (x) any making of any loan, advance or capital contributions to
or investment in any Person other than (A) loans, advances or capital
contributions to or investments in wholly-owned Subsidiaries or entities that
became wholly-owned Subsidiaries made in the ordinary course of business
consistent with past practice, (B) loans or advances made to employees in the
ordinary course of business consistent with past practice and (C) investments
made in the ordinary course of business consistent with past practice, (xi) any
material labor strike or dispute, other than routine individual grievances, or
any material activity or proceeding by a labor union or representative thereof
to organize any employees of the Company or any of its Subsidiaries, which
employees were not subject to a collective bargaining agreement at December 31,
2000, or any lockouts, strikes, slowdowns, work stoppages or threats thereof by
or with respect to such employees, or (xii) any agreement by the Company or any
of its Subsidiaries to perform any action described in clauses (i) through (xi)
above.

         Section 4.8 Information Supplied. None of the information supplied or
to be supplied by the Company specifically for inclusion or incorporation by
reference in (i) the Offer Documents, (ii) the Schedule 14D-9, (iii) the
information to be filed by the Company in connection with the Offer pursuant to
Rule 14f-1 promulgated under the Exchange Act (the "Information Statement") or
(iv) the Proxy Statement, will, in the case of the Offer Documents, the Schedule
14D-9 and the Information Statement, at the respective times the Offer
Documents, the Schedule 14D-9 and the Information Statement are filed with the
SEC or first published, sent or given to the Company's stockholders, or, in the
case of the Proxy Statement, at the time the Proxy Statement is first mailed to
the Company's stockholders or at the time of the Stockholders Meeting, contain
any untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary in order to make the statements
therein, in light of the circumstances under which they are made, not misleading
or necessary to correct any statement in any earlier communication with respect
to the solicitation of proxies for the Stockholders Meeting which has become
false or misleading. The Schedule 14D-9, the Information Statement and the Proxy
Statement will comply as to form in all material respects with the requirements
of the Exchange Act, except that no representation or warranty is made by the
Company with respect to statements made or incorporated by reference therein
based on information supplied by Parent or Sub specifically for inclusion or
incorporation by reference therein.

         Section 4.9 Compliance with Laws. The Company and its Subsidiaries have
been, and are, in compliance in all material respects with all applicable
statutes, laws, ordinances, regulations, rules, judgments, decrees or orders of
any Governmental Entity, except for any non-compliance that could not reasonably
be expected to have a Material Adverse Effect on the Company, and neither the
Company nor any of its Subsidiaries has received any notice from any
Governmental Entity or any other Person that either the Company or any of its
Subsidiaries is in violation of, or has violated, any applicable statutes, laws,
ordinances, regulations, rules, judgments, decrees or orders, except for
violations that could not reasonably be expected to have a Material Adverse
Effect on the Company. Each of the Company and its Subsidiaries has in

                                      -14-
   19

effect all Federal, state, local and foreign governmental Permits necessary for
it to own, lease or operate its properties and assets and to carry on its
business as now conducted, and there has occurred no default under any such
Permit, except for the absence of Permits and for defaults under Permits which
absence or defaults, individually or in the aggregate, could not reasonably be
expected to have a Material Adverse Effect on the Company.

         Section 4.10 Tax Matters. Except as set forth in Item 4.10 of the
Company Letter, (i) the Company and each of its Subsidiaries has timely filed
(after taking into account any extensions to file) all Tax Returns required to
be filed by them either on a separate or combined or consolidated basis, except
where the failure to timely file a Tax Return (other than a Federal or state
income Tax Return) would not reasonably be expected to have a Material Adverse
Effect on the Company; (ii) all such Tax Returns are complete and accurate,
except where the failure to be complete or accurate would not reasonably be
expected to have a Material Adverse Effect on the Company; (iii) each of the
Company and its Subsidiaries has paid or caused to be paid all Taxes as shown as
due on such Tax Returns and all material Taxes for which no return was filed,
except where the failure to do so would not reasonably be expected to have a
Material Adverse Effect on the Company; (iv) no deficiencies for any Taxes have
been asserted in writing, proposed in writing or assessed in writing against the
Company or any of its Subsidiaries that have not been paid or otherwise settled
or are not otherwise being challenged under appropriate procedures, except for
deficiencies the assertion, proposing or assessment of which would not
reasonably be expected to have a Material Adverse Effect on the Company; and (v)
no written requests for waivers of the time to assess any material Taxes of the
Company or its Subsidiaries are pending. Neither the Company nor any of its
Subsidiaries has taken or agreed to take any action or knows of any fact,
circumstance, plan or intention that is or would be reasonably likely to prevent
the Transaction from qualifying as a "reorganization" within the meaning of
Section 368(a) of the Code.

         Section 4.11 Liabilities. Except as set forth in the Company Filed SEC
Documents, neither the Company nor any of its Subsidiaries has any liabilities
or obligations of any nature (whether accrued, absolute, contingent or
otherwise) required by GAAP to be set forth on a consolidated balance sheet of
the Company and its Subsidiaries or in the notes thereto, other than liabilities
and obligations incurred in the ordinary course of business since December 31,
2000 and liabilities which would not, individually or in the aggregate,
reasonably be expected to have a Material Adverse Effect on the Company.

         Section 4.12 Litigation. Except as disclosed in Item 4.12 of the
Company Letter or in the Company Filed SEC Documents, there is no suit, action,
proceeding or investigation pending or, to the Knowledge of the Company,
threatened against the Company or any of its Subsidiaries that could reasonably
be expected to (i) have a Material Adverse Effect on the Company, (ii)
materially impair the ability of the Company to perform its obligations under
this Agreement or (iii) prevent or materially delay the consummation of the
Offer and/or the Merger; nor is there any outstanding judgment, order, writ,
injunction, rule or decree of any Governmental Entity or arbitrator outstanding
against the Company or any of its Subsidiaries having any such effect.

         Section 4.13 Benefit Plans. (a) Except as disclosed in the Company
Filed SEC Documents or Item 4.13(a) of the Company Letter or as required by law,
neither the Company nor any of its Subsidiaries has adopted or amended in any
material respect any Benefit Plan since

                                      -15-
   20

the date of the most recent audited financial statements included in the Company
Filed SEC Documents. Except as disclosed in Item 4.13(a) of the Company Letter
or in the Company Filed SEC Documents, there exist no material employment,
consulting, severance or termination agreements between the Company or any of
its Subsidiaries and any current or former officer, director, employee or
consultant of the Company or any of its Subsidiaries. The Company has made
available to Parent a copy of each Benefit Plan, including, without limitation,
each Severance Protection Agreement.

                  (b) Except as would not, individually or in the aggregate,
have a Material Adverse Effect on the Company, each ERISA Benefit Plan
maintained by the Company or any of its Subsidiaries has been maintained and
operated in compliance with its terms, the applicable requirements of applicable
law, including the Code and ERISA, and each ERISA Benefit Plan intended to be
"qualified" within the meaning of Section 401(a) of the Code has received a
favorable determination letter from the IRS. Except as disclosed in Item 4.13(b)
of the Company Letter, none of the Company, its Subsidiaries or any other person
or entity that together with the Company is treated as a single employer under
Section 414 of the Code (each, an "ERISA Affiliate") has at any time during the
five-year period preceding the date hereof contributed to any ERISA Benefit Plan
that is a "multiemployer plan" (as defined in Section 3(37) of ERISA) or
maintained any ERISA Benefit Plan that is subject to Title IV of ERISA or
Section 412 of the Code.

                  (c) Except as disclosed in Item 4.13(c) of the Company Letter,
as of the date of this Agreement there is no pending dispute, arbitration,
claim, suit or grievance involving a Benefit Plan (other than routine claims for
benefits payable under any such Benefit Plan) that would reasonably be expected
to have a Material Adverse Effect on the Company.

                  (d) No liability under Title IV or Section 302 of ERISA has
been incurred by the Company or any ERISA Affiliate that has not been satisfied
in full, and no condition exists that presents a material risk to the Company or
any ERISA Affiliate of incurring any such liability, other than any such
liability that would not have a Material Adverse Effect on the Company. Insofar
as the representation made in this Section 4.13(d) applies to Sections 4064,
4069 or 4204 of Title IV of ERISA, it is made with respect to any employee
benefit plan, program, agreement or arrangement subject to Title IV of ERISA to
which the Company or any ERISA Affiliate made, or was required to make,
contributions during the five-year period ending on the last day of the most
recent plan year ending prior to the Closing Date.

                  (e) Except as disclosed in Item 4.13(e) of the Company Letter,
no Benefit Plan provides medical, surgical, hospitalization or death benefits
(whether or not insured) for employees or former employees of the Company or any
of its Subsidiaries for periods extending beyond their retirement or other
termination of service, other than (i) coverage mandated by applicable law, (ii)
death benefits under any "pension plan," (iii) benefits the full cost of which
is borne by the current or former employee (or his or her beneficiary) or (iv)
exceptions which would not have a Material Adverse Effect on the Company.

                  (f) Item 4.13(f) of the Company Letter sets forth the
Company's good faith estimate of the payments that may be made under the Benefit
Plans that could constitute "excess parachute payments" within the meaning of
Section 280G of the Code.

                                      -16-
   21

         Section 4.14 State Takeover Statutes; Bylaws Provision; Rights
Agreement. The action of the Board of Directors of the Company in approving the
Offer (including the purchase of Shares pursuant to the Offer), the Merger, this
Agreement and the transactions contemplated by this Agreement is sufficient to
render inapplicable to the Offer, the Merger and this Agreement the provisions
of (i) Section 203 of the DGCL and (ii) Article IV of the Bylaws. The Company
has made available to Parent a complete and correct copy of the Company Rights
Agreement, including all current and proposed amendments and exhibits thereto.
The Board of Directors of the Company has taken all action necessary to amend
the Company Rights Agreement (subject only to the execution of such amendment by
the Company Rights Agent, which execution the Company shall cause to take place
within 48 hours of the date hereof) to provide that: (i) a Distribution Date (as
defined in the Company Rights Agreement) shall not occur, the Company Rights
shall not separate (to the extent the Company Rights Agreement otherwise
provides for such separation) or become exercisable and neither Parent nor Sub
shall become an Acquiring Person (as defined in the Company Rights Agreement) as
a result of the execution or delivery of this Agreement by Parent or Sub, the
public announcement of such execution and delivery or, provided that this
Agreement shall not have been terminated in accordance with Section 9.1 and
subject to the terms of this Agreement, the public announcement or the
commencement of the Offer or the consummation of the Offer and (ii) the Company
Rights shall cease to be exercisable and the Company Rights Agreement shall
terminate after the consummation of the Offer in accordance with the terms
thereof and the terms and conditions hereof, including the acceptance for
payment of, and the payment for all Shares tendered pursuant to the Offer. To
the Knowledge of the Company, no other "fair price," "moratorium," "control
share acquisition," or other anti-takeover statute or similar statute or
regulation, applies or purports to apply this Agreement, or the Offer, the
Merger or the other transactions contemplated by this Agreement.

         Section 4.15 Brokers. No broker, investment banker, financial advisor
or other person, other than Goldman, Sachs and Petrie Parkman, the fees and
expenses of which will be paid by the Company (and are reflected in an agreement
between Goldman, Sachs and the Company and an agreement between Petrie Parkman
and the Company, complete copies of which have been furnished to Parent), is
entitled to any broker's, finder's, financial advisor's or other similar fee or
commission in connection with the transactions contemplated by this Agreement
based upon arrangements made by or on behalf of the Company or any of its
Subsidiaries. If the transactions contemplated by this Agreement are
consummated, no such engagement letter obligates the Company to continue to use
the services or pay fees or expenses in connection with any future transaction.

         Section 4.16 Voting Requirements. Approval of the Merger requires the
affirmative vote of a majority of the outstanding Shares (the "Company
Stockholder Approval"). The Company Stockholder Approval is the only vote of the
holders of the Company's capital stock necessary to approve and adopt this
Agreement and the transactions contemplated hereby.

         Section 4.17 Environmental Matters.

                  Except as disclosed in Item 4.17 of the Company Letter:

                  (a) The Company and each of its Subsidiaries has been and is
in material compliance with all applicable Environmental Laws, including, but
not limited to, possessing all

                                      -17-
   22

permits, authorizations, licenses, exemptions and other governmental
authorizations required for its operations under applicable Environmental Laws,
except for such non-compliance that could not reasonably be expected to have a
Material Adverse Effect on the Company.

                  (b) There is no pending or, to the Knowledge of the Company,
threatened written claim, lawsuit, or administrative proceeding against the
Company or each of its Subsidiaries, under or pursuant to any Environmental Law,
that could reasonably be expected to have a Material Adverse Effect on the
Company. Neither the Company nor any of its Subsidiaries has received written
notice from any Person, including, but not limited to, any Governmental Entity,
alleging that the Company or any of its Subsidiaries has been or is in violation
or potentially in violation of any applicable Environmental Law or otherwise may
be liable under any applicable Environmental Law, which violation or liability
is unresolved and could reasonably be expected to have a Material Adverse Effect
on the Company. Neither the Company nor any of its Subsidiaries has received any
written request for information from any Person, including but not limited to
any Governmental Entity, related to liability under or compliance with any
applicable Environmental Law, except for such matters as would not, if they
matured into a claim against the Company or any of its Subsidiaries, have a
Material Adverse Effect on the Company.

                  (c) With respect to the real property that is currently owned,
leased or operated by the Company or any of its Subsidiaries, there have been no
spills, discharges or releases (as such term is defined by the Comprehensive
Environmental Response, Compensation and Liability Act, 42, U.S.C. 9601, et
seq.) of Hazardous Substances or any other contaminant or pollutant on or
underneath any of such real property that could reasonably be expected to have a
Material Adverse Effect on the Company.

                  (d) With respect to real property that was formerly owned,
leased or operated by the Company or any of its Subsidiaries or any of their
predecessors in interest, to the Knowledge of the Company, there were no spills,
discharges or releases (as such term is defined by the Comprehensive
Environmental Response, Compensation and Liability Act, 42, U.S.C. 9601, et
seq.) of Hazardous Substances or any other contaminant or pollutant on or
underneath any of such real property during or prior to the Company's or any of
its Subsidiaries' ownership or operation of such real property that could
reasonably be expected to result in a Material Adverse Effect on the Company.

                  (e) Except as disclosed on Item 4.17(e) of the Company Letter,
neither the Company nor any of its Subsidiaries has entered into any written
agreement or incurred any material legal or monetary obligation that may require
them to pay to, reimburse, guarantee, pledge, defend, indemnify or hold harmless
any Person from or against any liabilities or costs arising out of or related to
the generation, manufacture, use, transportation or disposal of Hazardous
Substances, or otherwise arising in connection with or under Environmental Laws,
other than in each case exceptions which would not reasonably be expected to
have a Material Adverse Effect on the Company.

                  (f) To the Knowledge of the Company, neither the Company nor
any of its Subsidiaries has disposed or arranged for the disposal of Hazardous
Substances (or any waste or substance containing Hazardous Substances) at any
location that is: (i) listed on the Federal National Priorities List ("NPL") or
identified on the CERCLIS, each established pursuant to the

                                      -18-
   23

Comprehensive Environmental Response, Compensation and Liability Act, 42, U.S.C.
9601, et seq.; (ii) listed on any state list of hazardous waste sites that is
analogous to the NPL or CERCLIS; or (iii) has been subject to environmental
investigation or remediation, other than, in each case, exceptions which would
not reasonably be expected to have a Material Adverse Effect on the Company.

         Section 4.18 Contracts; Debt Instruments. (a) Item 4.18(a) of the
Company Letter and the Company's Annual Report on Form 10-K for the year ended
December 31, 2000 (the "2000 10-K") together set forth a true and complete list
of (i) all material agreements to which the Company or any of its Subsidiaries
is a party; (ii) all agreements relating to the incurring of indebtedness
(including sale and leaseback and capitalized lease transactions and other
similar financing transactions) providing for payment or repayment in excess of
$10 million; (iii) the exhibits contained or incorporated by reference in the
2000 10-K contain or incorporate by reference all of the contracts required to
be included therein; (iv) all agreements requiring capital expenditures in
excess of $5 million individually (other than agreements relating to the
drilling, completion and connection of wells in the ordinary course of business
(including all related service contracts) and agreements relating to joint
operation, development and exploration entered into in the ordinary course of
business); and (v) any non-competition agreements or any other agreements or
obligations which purport to limit in any material respect the manner in which,
or the localities in which, all or any substantial portion of the business of
the Company and its Subsidiaries, taken as a whole, is conducted (the
agreements, contracts and obligations specified above, collectively the "Company
Contracts"). All Company Contracts are valid and in full force and effect on the
date hereof except to the extent they have previously expired in accordance with
their terms or if the failure to be in full force and effect, individually and
in the aggregate, would not have a Material Adverse Effect on the Company.
Neither the Company nor any of its Subsidiaries has violated any provision of,
or committed or failed to perform any act which with or without notice, lapse of
time or both would constitute a default under the provisions of, any Company
Contract that could reasonably be expected to have a Material Adverse Effect on
the Company.

                  (b) Except as described in Item 4.18(b) of the Company Letter
or in the Company SEC Documents, the execution and delivery of this Agreement
and the consummation of the transactions contemplated hereby will not (i) result
in any material payment (including severance, unemployment compensation, tax
gross-up, bonus or otherwise) becoming due to any current or former director,
officer, employee or independent contractor of the Company or any of its
Subsidiaries, from the Company or any of its Subsidiaries under any Company
Stock Plan, Benefit Plan, agreement or otherwise, (ii) materially increase any
benefits otherwise payable under any Company Stock Plan, Benefit Plan, agreement
or otherwise or (iii) result in the acceleration of the time of payment,
exercise or vesting of any such material benefits.

         Section 4.19 Title to Properties. Except as set forth in Item 4.19 of
the Company Letter:

                  (a) Each of the Company and its Subsidiaries has good and
marketable title to, or valid leasehold interests in, all its properties and
assets, free and clear of all Liens, except for defects in title, easements,
restrictive covenants and similar encumbrances or impediments that, in the
aggregate, do not and could not reasonably be expected to have a Material
Adverse Effect on the Company.

                                      -19-
   24

                  (b) Each of the Company and its Subsidiaries has complied in
all material respects with the terms of all material leases to which it is a
party and under which it is in occupancy, and all such leases are in full force
and effect, except for such non-compliance that could not reasonably be expected
to have a Material Adverse Effect on the Company. To the Knowledge of the
Company, each of the Company and each of its Subsidiaries enjoys peaceful and
undisturbed possession under all such leases, except for such noncompliance that
could not reasonably be expected to have a Material Adverse Effect on the
Company.

         Section 4.20 Intellectual Property. (a) As used in this Agreement,
"Company Intellectual Property" means all of the following which are necessary
to conduct the business of the Company and its Subsidiaries as presently
conducted: (i) trademarks, trade dress, service marks, copyrights, logos, trade
names, corporate names and all registrations and applications to register the
same; (ii) patents and pending patent applications; (iii) all computer software
programs, databases and compilations; and (iv) all material licenses and
agreements to which the Company or any of its Subsidiaries is a party which
relate to any of the foregoing.

                  (b) Except as disclosed in Item 4.20(b) of the Company Letter,
the Company or its Subsidiaries owns or has the right to use all Company
Intellectual Property necessary to conduct the Company's business as presently
conducted, except as would not, individually or in the aggregate, be expected to
have a Material Adverse Effect on the Company.

                  (c) Except as disclosed in Item 4.20(b) of the Company Letter,
to the Knowledge of the Company, the conduct of the Company's and its
Subsidiaries' business or the use of the Company Intellectual Property does not
infringe, violate, misappropriate or misuse any intellectual property rights or
any other proprietary right of any Person or give rise to any obligations to any
Person as a result of co-authorship, except in each case for exceptions which
would not, individually or in the aggregate, be expected to have a Material
Adverse Effect on the Company.

         Section 4.21 Condition of Assets. All of the material property, plant
and equipment of the Company and its Subsidiaries, has in all material respects
been maintained in reasonable operating condition and repair, ordinary wear and
tear excepted, and is in all material respects, sufficient to permit the Company
and its Subsidiaries to conduct their operations in the ordinary course of
business in a manner consistent with their past practices.

         Section 4.22 Derivative Transactions.

                  (a) Except as set forth in Section 4.22(a) of the Company
Letter, neither the Company nor its Subsidiaries has entered into any material
Derivative Transactions (as defined below) since December 31, 2000 that have a
continuing financial liability or obligation. All Derivative Transactions
entered into by the Company or any of its Subsidiaries that are currently open
were entered into in material compliance with applicable rules, regulations and
policies of all regulatory authorities.

                  (b) For purposes of this Section 4.22, "Derivative
Transactions" means derivative transactions within the coverage of FAS 133,
including any swap transaction, option, warrant, forward purchase or sale
transaction, futures transaction, cap transaction, floor transaction or

                                      -20-
   25

collar transaction relating to one or more currencies, commodities, bonds,
equity securities, loans, interest rates, credit-related events or conditions or
any indexes, or any other similar transaction (including any option with respect
to any of these transactions) or combination of any of these transactions,
including collateralized mortgage obligations or other similar instruments or
any debt or equity instruments evidencing or embedding any such types of
transactions, and any related credit support, collateral, transportation or
other similar arrangements or agreements related to such transactions.

                                   ARTICLE V
                REPRESENTATIONS AND WARRANTIES OF PARENT AND SUB

         Parent and Sub represent and warrant to the Company as follows:

         Section 5.1 Organization. Parent and each of its Significant
Subsidiaries is duly organized, validly existing and in good standing under the
laws of the jurisdiction of its organization and has requisite power and
authority to carry on its business as now being conducted, except where the
failure to be so organized, existing and in good standing or to have such power
and authority would not reasonably be expected to have a Material Adverse Effect
on Parent. Parent and each of its Significant Subsidiaries is duly qualified or
licensed to do business and in good standing in each jurisdiction in which the
nature of its business or the ownership or leasing of its properties makes such
qualification or licensing necessary, except in such jurisdictions where the
failure to be so duly qualified or licensed and in good standing would not
reasonably be expected to have a Material Adverse Effect on Parent or prevent or
materially delay the consummation of the Offer and/or the Merger. Parent has
delivered to the Company complete and correct copies of its Certificate of
Incorporation and Bylaws and has made available to the Company the charter and
bylaws (or similar organizational documents) of each of its Significant
Subsidiaries.

         Section 5.2 Capital Structure. Except as set forth in Item 5.2 of the
Parent Letter, the authorized capital stock of Parent consists of 960,000,000
shares of common stock (the "Parent Shares") and 30,000,000 shares of preferred
stock. At the close of business on March 23, 2001, (i) 484,040,320 Parent Shares
were issued and outstanding, all of which were validly issued, fully paid and
nonassessable and free of preemptive rights and (ii) 6,311,910 Parent Shares
were held by Parent in its treasury. As of the close of business on April 24,
2001, there were 25,554,954 Parent Shares reserved for issuance pursuant to
outstanding options to purchase Parent Shares (the "Parent Stock Options")
granted under Parent's 1996 Stock Plan, its Stock Plan for Non-Officer
Employees, its 1996 Stock Plan for Non-Employee Directors, and the Williams
International Stock Plan (the "Parent Stock Incentive Plans"), and, as of the
close of business on February 28, 2001, there were 15,122,521 Parent Shares
reserved for the grant of additional awards under Parent Stock Incentive Plans.
The numbers of shares of capital stock and options described in the immediately
preceding sentences have not materially changed as of the date of this
Agreement, except for adjustments made in connection with the April 23, 2001
spin-off of Williams Communications Group, Inc. from Parent. As of the date of
this Agreement, except as set forth above, no Parent Shares were issued,
reserved for issuance or outstanding and there are not any phantom stock or
other contractual rights the value of which is determined in whole or in part by
the value of any capital stock of Parent ("Parent Stock Equivalents"). There are
no outstanding stock appreciation rights with respect to the capital

                                      -21-
   26

stock of Parent. Each outstanding Parent Share is, and each Parent Share which
may be issued pursuant to Parent Stock Plans will be, when issued, duly
authorized, validly issued, fully paid and nonassessable and not subject to
preemptive rights. There are no outstanding bonds, debentures, notes or other
indebtedness of Parent having the right to vote (or convertible into, or
exchangeable for, securities having the right to vote) on any matter on which
Parent's stockholders may vote. Except as set forth above or in Item 5.3 of the
Parent Letter, as of the date of this Agreement, there are no securities,
options, warrants, calls, rights, commitments, agreements, arrangements or
undertakings of any kind to which Parent or any of its Significant Subsidiaries
is a party or by which any of them is bound obligating Parent or any of its
Significant Subsidiaries to issue, deliver or sell or create, or cause to be
issued, delivered or sold or created, additional shares of capital stock or
other voting securities or Parent Stock Equivalents of Parent or of any of its
Significant Subsidiaries or obligating Parent or any of its Significant
Subsidiaries to issue, grant, extend or enter into any such security, option,
warrant, call, right, commitment, agreement, arrangement or undertaking.

                  As of the date of this Agreement, there are no outstanding
contractual obligations of Parent or any of its Significant Subsidiaries to
repurchase, redeem or otherwise acquire any shares of capital stock of Parent or
any of its Significant Subsidiaries.

         Section 5.3 Authority. Each of Parent and Sub has requisite corporate
power and authority to execute and deliver this Agreement and to consummate the
transactions contemplated hereby. The execution, delivery and performance of
this Agreement by each of Parent and Sub and the consummation by it of the
transactions contemplated hereby have been duly authorized by all necessary
corporate and stockholder action on the part of each of Parent and Sub. This
Agreement has been duly executed and delivered by each of Parent and Sub and
(assuming the valid authorization, execution and delivery of this Agreement by
the Company) constitutes the valid and binding obligation of each of Parent and
Sub enforceable against it in accordance with its terms, except that such
enforceability (i) may be limited by bankruptcy, insolvency, moratorium or other
similar laws affecting or relating to the enforcement of creditors' rights
generally and (ii) is subject to general principles of equity.

         Section 5.4 Consents and Approvals; No Violations. Except for filings,
permits, authorizations, consents and approvals as may be required under, and
other applicable requirements of, the Exchange Act, the Securities Act, the HSR
Act, the DGCL, the laws of other states in which Parent is qualified to do or is
doing business, state takeover laws and foreign and supranational laws relating
to antitrust and anticompetition clearances, and except as may be required in
connection with the Taxes described in Section 7.7, neither the execution and
delivery of this Agreement, nor the consummation of the transactions
contemplated by this Agreement and compliance with the provisions of this
Agreement will conflict with or result in any violation of, or default (with or
without notice or lapse of time, or both) under, or give rise to a right of
termination, cancellation or acceleration of any obligation or to loss of a
material benefit under, or result in the creation of any Lien upon, any of the
properties or assets of Parent or any of its Subsidiaries, (i) the certificate
of incorporation or bylaws of Parent or the comparable charter or organizational
documents of any of Parent's Significant Subsidiaries, (ii) require any filing
with, or permit, authorization, consent or approval of, any Governmental Entity
(except where the failure to obtain such permits, authorizations, consents or
approvals or to make such filings would not reasonably be expected to have a
Material Adverse Effect on

                                      -22-
   27

Parent or prevent or materially delay the consummation of the Offer and/or the
Merger), (iii) result in a violation or breach of, or constitute (with or
without due notice or lapse of time or both) a default (or give rise to any
right of termination, amendment, cancellation or acceleration) under, any of the
terms, conditions or provisions of any note, bond, mortgage, indenture, lease,
license, contract, agreement or other instrument or obligation to which Parent
or any of its Subsidiaries is a party or by which any of them or any of their
properties or assets may be bound or (iv) violate any order, writ, injunction,
decree, statute, rule or regulation applicable to Parent, Sub, any of its
Significant Subsidiaries or any of their properties or assets, except in the
case of clauses (iii) or (iv) for violations, breaches or defaults that would
not reasonably be expected to have a Material Adverse Effect on Parent or
prevent or materially delay the consummation of the Offer and/or the Merger.

         Section 5.5 SEC Documents and Other Reports. Parent has filed with the
SEC all documents required to be filed by it since April 1, 1998 under the
Securities Act or the Exchange Act (the "Parent SEC Documents"). As of their
respective filing dates, the Parent SEC Documents complied in all material
respects with the requirements of the Securities Act or the Exchange Act, as the
case may be, each as in effect on the date so filed, and at the time filed with
the SEC none of the Parent SEC Documents contained any untrue statement of a
material fact or omitted to state a material fact required to be stated therein
or necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading. The financial statements of Parent
included in the Parent SEC Documents comply as of their respective dates in all
material respects with the then applicable accounting requirements and the
published rules and regulations of the SEC with respect thereto, have been
prepared in accordance with GAAP (except in the case of the unaudited
statements, as permitted by Form 10-Q under the Exchange Act) applied on a
consistent basis during the periods involved (except as may be indicated therein
or in the notes thereto) and fairly present the consolidated financial position
of Parent and its consolidated Subsidiaries as at the dates thereof and the
consolidated results of their operations and their consolidated cash flows for
the periods then ended (subject, in the case of unaudited statements, to normal
year-end audit adjustments and to any other adjustments described therein).

         Section 5.6 Absence of Material Adverse Change. Except as disclosed in
Item 5.7 of the Parent Letter or in the documents filed by Parent with SEC and
publicly available prior to the date of the Agreement (the "Parent Filed SEC
Documents"), since December 31, 2000 Parent and its Subsidiaries have conducted
their respective businesses in all material respects only in the ordinary course
consistent with past practice, and there has not been (i) any Material Adverse
Change with respect to Parent, (ii) except for (a) ordinary quarterly dividends
paid or payable to stockholders of Parent and (b) the distribution of shares of
Williams Communications Group to holders of Parent Shares, any declaration,
setting aside or payment of any dividend or other distribution with respect to
its capital stock or any redemption, purchase or other acquisition of any of its
capital stock, (iii) any split, combination or reclassification of any of its
capital stock or any issuance or the authorization of any issuance of any other
securities in respect of, in lieu of or in substitution for shares of its
capital stock, or (iv) any change in accounting methods, principles or practices
by Parent materially affecting its assets, liabilities or business, except
insofar as may have been required by a change in generally accepted accounting
principles.

                                      -23-
   28

         Section 5.7 Information Supplied. None of the information supplied or
to be supplied by Parent or Sub specifically for inclusion or incorporation by
reference in (i) the Offer Documents, (ii) the Schedule 14D-9, (iii) the
Information Statement, (iv) the Proxy Statement or (v) the Form S-4 will, in the
case of the Offer Documents, the Schedule 14D-9 and the Information Statement,
at the respective times the Offer Documents, the Schedule 14D-9 and the
Information Statement are filed with the SEC or first published, sent or given
to the Company's stockholders, contain any untrue statement of a material fact
or omit to state any material fact required to be stated therein or necessary in
order to make the statements therein, in light of the circumstances under which
they are made, not misleading or, in the case of the Form S-4, at the time it
becomes effective under the Securities Act, or, in the case of the Proxy
Statement, if any, at the time the Proxy Statement is first mailed to the
Company's stockholders or at the time of the Stockholders Meeting, be false or
misleading with respect to any material fact, or omit to state any material fact
required to be stated therein or necessary in order to make the statements made
therein, in the light of the circumstances under which they are made, not
misleading or necessary to correct any statement in any earlier communication
with respect to the solicitation of proxies for the Stockholders Meeting which
has become false or misleading, except that no representation or warranty is
made by Parent or Sub in connection with any of the foregoing with respect to
statements made or incorporated by reference therein based on information
supplied by the Company or any of its representatives specifically for inclusion
or incorporation by reference therein. The Offer Documents will comply as to
form in all material respects with the requirements of the Exchange Act, except
that no representation or warranty is made by Parent or Sub in connection with
any of the foregoing with respect to statements made or incorporated by
reference therein based on information supplied by the Company or any of its
representatives specifically for inclusion or incorporation by reference
therein.

         Section 5.8 Compliance with Laws. Parent and its Subsidiaries have been
and are, in compliance in all material respects with all applicable statutes,
laws, ordinances, regulations, rules, judgments, decrees or orders of any
Governmental Entity, except for any non-compliance that could not reasonably be
expected to have a Material Adverse Effect on Parent, and neither Parent nor any
of its Subsidiaries has received any notice from any Governmental Entity or any
other Person that either Parent or any of its Subsidiaries is in violation of,
or has violated, any applicable statutes, laws, ordinances, regulations, rules,
judgments, decrees or orders, except for violation that could not reasonably be
expected to have a Material Adverse Effect on Parent. Each of Parent and its
Subsidiaries has in effect all Federal, state, local and foreign governmental
Permits necessary for it to own, lease or operate properties and assets and to
carry on its business as now conducted, and there has occurred no default under
any such Permit, except for the absence of Permits and for defaults under
Permits which absence or defaults, individually or in the aggregate, could not
reasonably be expected to have a Material Adverse Effect on Parent.

         Section 5.9 Parent Shares. All of the Parent Shares issuable in
exchange for Shares in the Merger in accordance with this Agreement will be,
when so issued, duly authorized, validly issued, fully paid and non-assessable
and free of preemptive rights. The issuance of such Parent Shares will be
registered under the Securities Act and registered or exempt from registration
under applicable state securities laws.

         Section 5.10 Reorganization. Neither Parent nor any of its Subsidiaries
has taken or agreed to take any action or knows of any fact, circumstance, plan
or intention that is or would

                                      -24-
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be reasonably likely to prevent the Transaction from qualifying as a
"reorganization" within the meaning of Section 368(a) of the Code.

         Section 5.11 Liabilities. Except as set forth in the Parent Filed SEC
Documents, neither Parent nor any of its Subsidiaries has any liabilities or
obligations of any nature (whether accrued, absolute, contingent or otherwise)
required by GAAP to be set forth on a consolidated balance sheet of Parent and
its Subsidiaries or in the notes thereto, other than liabilities and obligations
incurred in the ordinary course of business since December 31, 2000 and
liabilities which would not, individually or in the aggregate, reasonably be
expected to have a Material Adverse Effect on Parent.

         Section 5.12 Interim Operations of Sub. Sub was formed solely for the
purpose of engaging in the transactions contemplated hereby, has engaged in no
other business activities and has conducted its operations only as contemplated
hereby.

         Section 5.13 Litigation. Except as disclosed in Item 5.13 of the Parent
Letter or in the Parent Filed SEC Documents, there is no suit, action,
proceeding or investigation pending against Parent or any of its Subsidiaries
that would reasonably be expected to have a Material Adverse Effect on Parent or
prevent or materially delay the consummation of the Offer and/or the Merger.
Except as disclosed in Item 5.13 of the Parent Letter or in the Parent Filed SEC
Documents, neither Parent nor any of its Subsidiaries is subject to any
outstanding judgment, order, writ, injunction or decree that would reasonably be
expected to have a Material Adverse Effect on Parent or prevent or materially
delay the consummation of the Offer and/or the Merger.

         Section 5.14 California Exposure. Based on the facts and circumstances
known to Parent on the date of this Agreement, Parent believes that the reserves
reflected in its most recent financial statements are adequate in all material
respects in relation to Parent's credit, regulatory or litigation exposure
arising from the sale of natural gas or electricity in the State of California.

         Section 5.15 Brokers. No broker, investment banker, financial advisor
or other person, other than Merrill Lynch & Co., the fees and expenses of which
will be paid by Parent, is entitled to any broker's, finder's, financial
advisor's or other similar fee or commission in connection with the transactions
contemplated by this Agreement based upon arrangements made by or on behalf of
Parent or Sub.

                                   ARTICLE VI
                    COVENANTS RELATING TO CONDUCT OF BUSINESS

         Section 6.1 Conduct of Business Pending the Merger.

                  (a) Conduct of Business by the Company Pending the Merger.
During the period from the date of this Agreement until the earlier of the
Effective Time or such time as Parent's designees shall constitute a majority of
the Board of Directors of the Company, the Company shall, and shall cause each
of its Subsidiaries to, in all material respects, except as contemplated by this
Agreement, carry on its business in the ordinary course as currently conducted.
Without limiting the generality of the foregoing, and except as otherwise
contemplated by this Agreement (including, without limitation, as permitted or
required by Section 7.9 or Section 7.11), during

                                      -25-
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such period, the Company shall not, and shall not permit any of its Subsidiaries
to, without the prior written consent of Parent (which consent shall not be
unreasonably withheld or delayed):

                           (i) (A) declare, set aside or pay any dividends on,
                  or make any other distributions in respect of, any of its
                  capital stock, except for dividends by a Subsidiary of the
                  Company to its parent or (B) split, combine or reclassify any
                  of its capital stock or issue or authorize the issuance of any
                  other securities in respect of, in lieu of or in substitution
                  for shares of its capital stock;

                           (ii) issue, deliver, sell, pledge or otherwise
                  encumber any shares of its capital stock, any other voting
                  securities or any securities convertible into, or any rights,
                  warrants or options to acquire, any such shares, voting
                  securities or convertible securities, other than (i) the
                  issuance of Shares upon exercise of Company Stock Options
                  outstanding on the date hereof or (ii) purchase, redeem or
                  otherwise acquire any shares of capital stock of the Company
                  or any of its Subsidiaries or any other securities thereof or
                  any rights, warrants or options to acquire any such shares or
                  other securities;

                           (iii) amend its Restated Certificate of Incorporation
                  or Bylaws or other similar organizational documents;

                           (iv) except as disclosed in Item 6.1(a) of the
                  Company Letter, acquire, or agree to acquire, in a single
                  transaction or in a series of related transactions, any
                  business or assets, other than transactions that are in the
                  ordinary course of business, or which involve assets having a
                  purchase price not in excess of $5 million individually or $10
                  million in the aggregate;

                           (v) make or agree to make any new capital expenditure
                  other than expenditures approved by the Board of Directors of
                  the Company and within the Company's capital budget for fiscal
                  2001, a true, complete and correct copy of which has been
                  provided to Parent; provided, however, that no individual
                  capital expenditure by the Company pursuant to a single
                  authority for expenditure may exceed $2.5 million;

                           (vi) except as disclosed in Item 6.1(a) of the
                  Company Letter, sell, lease, license, encumber or otherwise
                  dispose of, or agree to sell, lease, license, encumber or
                  otherwise dispose of, any of its assets, other than
                  transactions that are in the ordinary course of business or
                  which involve assets having a current value not in excess of
                  $1 million individually or $5 million in the aggregate;

                           (vii) except as disclosed in Item 6.1(a) of the
                  Company Letter: (i) increase the salary or wages payable or to
                  become payable to its directors, officers or employees, except
                  for increases required under employment agreements existing on
                  the date hereof, and except for increases for officers and
                  employees not in excess of 10% of such person's salary or
                  wages as in effect at the date of this Agreement; or (ii)
                  enter into, modify or amend any employment or severance
                  agreement with, or establish, adopt, enter into or amend any
                  bonus, profit sharing,

                                      -26-
   31

                  thrift, stock option, restricted stock, pension, retirement,
                  deferred compensation, employment, termination or severance
                  plan or agreement or material policy or arrangement for the
                  benefit of, any director, officer or employee, except as may
                  be required by the terms of any such plan, agreement, policy
                  or arrangement or to comply with applicable law or as
                  contemplated by this Agreement;

                           (viii) except as may be required as a result of a
                  change in law or in generally accepted accounting principles,
                  make any material change in its method of accounting;

                           (ix) make any material Tax election (unless required
                  by law) or enter into any settlement or compromise of any
                  material Tax liability that, in either case, could reasonably
                  be expected to have a Material Adverse Effect on the Company;

                           (x) (i) mortgage or otherwise encumber or subject to
                  any Lien the Company's or its Subsidiaries', properties or
                  assets, except in the ordinary course of business consistent
                  with past practice or pursuant to existing contracts or
                  commitments, or (ii) except in the ordinary course of business
                  consistent with past practice or pursuant to existing
                  contracts or commitments, license any of the Company's
                  Intellectual Property;

                           (xi) pay, discharge or satisfy any claims,
                  liabilities or obligations (absolute, accrued, asserted or
                  unasserted, contingent or otherwise), other than the payment,
                  discharge or satisfaction, in the ordinary course of business
                  consistent with past practice and in accordance with their
                  terms, or (i) liabilities reflected or reserved against in, or
                  contemplated by, the most recent consolidated financial
                  statements (or the notes thereto) of the Company included in
                  the Company SEC Documents, (ii) liabilities incurred in the
                  ordinary course of business consistent with past practice, or
                  (iii) other liabilities or obligations not to exceed in the
                  aggregate $2,500,000;

                           (xii) (i) incur any Indebtedness or guarantee any
                  such Indebtedness of another Person, issue or sell any debt
                  securities or warrants or other rights to acquire any debt
                  securities of the Company or any of its Subsidiaries,
                  guarantee any debt securities of another Person, enter into
                  any "Keep Well" or other agreement to maintain any financial
                  statement condition of another Person or enter into any
                  arrangement having the economic effect of any of the
                  foregoing, except for borrowings incurred in the ordinary
                  course of business (or to refund existing or maturing
                  indebtedness) consistent with past practice and except for
                  intercompany indebtedness between the Company and any of its
                  wholly-owned Subsidiaries or between such Subsidiaries and
                  except for Indebtedness, guarantees and similar commitments
                  which do not exceed $10 million in the aggregate, or (ii) make
                  any loans, advances or capital contributions to, or
                  investments in, any other Person, except in the ordinary
                  course of business or pursuant to an agreement existing on the
                  date hereof or loans, advances, capital contributions or
                  investments which do not exceed $10 million in the aggregate;
                  or

                                      -27-
   32

                           (xiii) enter into or authorize any contract,
                  agreement or binding commitment to do any of the foregoing.

                  (b) Conduct of Business by the Parent Pending the Merger.
During the period from the date of this Agreement until the Effective Time,
Parent shall, and shall cause each of its Subsidiaries to, in all material
respects, except as contemplated by this Agreement, carry on its business in the
ordinary course as currently conducted. Without limiting the generality of the
foregoing, and except as otherwise contemplated by this Agreement, during such
period, Parent shall not, and shall not permit any of its Subsidiaries to,
without the prior written consent of the Company (which consent shall not be
unreasonably withheld or delayed):

                           (i) make any change in or amendment to Parent's
                  Certificate of Incorporation that changes any material term or
                  provision of the Parent Shares;

                           (ii) make any material change in or amendment to
                  Sub's Certificate of Incorporation;

                           (iii) engage in any material repurchase at a premium,
                  recapitalization, restructuring or reorganization with respect
                  to Parent's capital stock, including, without limitation, by
                  way of any extraordinary dividend on, or other extraordinary
                  distributions with respect to, Parent's capital stock;

                           (iv) acquire by merging or consolidating with, or by
                  purchasing a substantial portion of the assets of or equity
                  in, or by any other manner, any person or any business or
                  division thereof, or otherwise acquire any assets, unless such
                  acquisition or the entering into of a definitive agreement
                  relating to or the consummation of such transaction would not
                  (A) impose any material delay in the obtaining of, or
                  materially increase the risk of not obtaining, any
                  authorizations, consents, orders, declarations or approvals of
                  any Governmental Entity necessary to consummate the Offer, the
                  Merger or the expiration or termination of any applicable
                  waiting period, (B) materially increase the risk of any
                  Governmental Entity entering an order prohibiting the
                  consummation of the Offer or the Merger or (C) increase the
                  risk of not being able to remove any such order on appeal or
                  otherwise; or

                           (v) enter into any contract or agreement to do any of
                  the foregoing.

         Section 6.2 No Solicitation; Acquisition Proposals. (a) From the date
of this Agreement until the Effective Time or, if earlier, the termination of
this Agreement in accordance with its terms, (1) the Company shall, and the
Company shall cause its and its Subsidiaries' respective Representatives to,
immediately cease and terminate any existing solicitation, initiation, knowing
encouragement, discussion or negotiation with any Third Party conducted
heretofore by the Company, its Subsidiaries or their respective Representatives
with respect to any Acquisition Proposal and (2) the Company shall not, and the
Company shall cause its and its Subsidiaries' respective Representatives not to,
directly or indirectly, (i) solicit, initiate or knowingly encourage (including
by way of furnishing non-public information), or knowingly take any other action
to facilitate, any inquiries or the making or submission of any proposal that
constitutes, or

                                      -28-
   33

may reasonably be expected to lead to, any Acquisition Proposal; (ii) enter into
any agreement with respect to any Acquisition Proposal or enter into any
agreement requiring the Company to abandon, terminate or fail to consummate the
acquisition of Shares pursuant to the Offer or the Merger; (iii) participate or
engage in any discussions or negotiations with, or disclose or provide any
non-public information or data relating to the Company or its Subsidiaries to
any Third Party relating to an Acquisition Proposal (except as required by legal
process), or knowingly facilitate any effort or attempt to make or implement an
Acquisition Proposal or accept an Acquisition Proposal; or (iv) enter into any
letter of intent, agreement or similar document relating to any Acquisition
Proposal.

                  (b) Notwithstanding the restrictions set forth in Section
6.2(a), if, at any time prior to the acquisition of Shares pursuant to the
Offer, (1) the Company has received an unsolicited bona fide written proposal
from a Third Party relating to an Acquisition Proposal (under circumstances in
which the Company has complied in all material respects with its obligations
under Section 6.2(a)) and (2) the Board of Directors of the Company concludes in
good faith (after consultation with a financial advisor of nationally recognized
reputation and after receiving the advice of its outside counsel) (i) that such
Acquisition Proposal may reasonably constitute a Superior Proposal and (ii) that
the failure to provide such information or participate in such negotiations or
discussions would result in a breach by the Board of Directors of the Company of
its fiduciary duties to the Company's stockholders under applicable law, the
Company may, subject to its giving Parent 24 hours prior written notice of the
identity of such Third Party and, to the extent known, the terms and conditions
of such Acquisition Proposal and of the Company's intention to furnish nonpublic
information to, or enter into discussions or negotiations with, such Third
Party, (x) furnish information with respect to the Company and its Subsidiaries
to any Third Party pursuant to a customary confidentiality agreement containing
terms not materially less restrictive than the terms of the Confidentiality
Agreement dated March 9, 2001, entered into between the Company and Parent, as
the same may be amended, supplemented or modified (the "Confidentiality
Agreement"), provided that a copy of all such information is delivered
simultaneously to Parent if it has not previously been so furnished to Parent,
and (y) participate in discussions or negotiations regarding such proposal or
take any of the actions described in Section 6.2(a)(2)(i) through (iv),

                  (c) The Company shall within 24 hours notify and advise Parent
orally and in writing of any Acquisition Proposal and the terms and conditions
of such Acquisition Proposal. The Company shall inform Parent on a prompt and
current basis of the status of any discussions regarding, or relating to, any
Acquisition Proposal with a Third Party (including amendments and proposed
amendments) and, as promptly as practicable, of any change in the price,
structure or form of the consideration or material terms of and conditions
regarding the Acquisition Proposal. In fulfilling its obligations under this
paragraph (c) of this Section 6.2, the Company shall provide promptly to Parent
copies of all material written correspondence or material written documents
furnished to the Company or its Representatives by or on behalf of such Third
Party.

                  (d) The Company agrees that it will promptly inform its and
its Subsidiaries' respective Representatives of the obligations undertaken in
this Section 6.2.

                                      -29-
   34

                  (e) Nothing contained in this Agreement shall prohibit the
Company from taking and disclosing to its stockholders a position as required by
Rule 14d-9 or Rule 14e-2(a) promulgated under the Exchange Act.

                  (f) For purposes of this Agreement,

                           "Acquisition Proposal" means any inquiry, offer,
                           proposal, indication of interest, signed agreement or
                           completed action, as the case may be, by any Third
                           Party which relates to a transaction or series of
                           transactions (including any merger, consolidation,
                           recapitalization, liquidation or other direct or
                           indirect business combination) involving the Company
                           or the issuance or acquisition of 20% or more of the
                           outstanding Shares or any tender or exchange offer
                           that if consummated would result in any Person,
                           together with all affiliates thereof, Beneficially
                           Owning 20% or more of the outstanding Shares, or the
                           acquisition, license, purchase or other disposition
                           of a substantial portion of the business or assets of
                           the Company outside the ordinary course of business;
                           and

                           "Superior Proposal" means any bona fide written
                           Acquisition Proposal (provided that for the purposes
                           of this definition, the applicable percentages in the
                           definition of Acquisition Proposal shall be fifty
                           percent (50%) as opposed to twenty percent (20%)), on
                           its most recently amended or modified terms, if
                           amended or modified, which the Board of Directors of
                           the Company determines in its good faith judgment
                           (after receipt of the advice of a financial advisor
                           of nationally recognized reputation and receiving
                           advice of its outside counsel), taking into account,
                           among other things, all legal, financial, regulatory
                           and other aspects of the proposal and the Third Party
                           making the proposal (i) would, if consummated, result
                           in a transaction that is more favorable to the
                           Company's stockholders (in their capacities as
                           stockholders), from a financial point of view, than
                           the transactions contemplated by this Agreement and
                           (ii) is reasonably capable of being completed.

         Section 6.3 Third Party Standstill Agreements. During the period from
the date of this Agreement through the Effective Time, the Company shall enforce
and shall not terminate, amend, modify or waive any standstill provision of any
confidentiality or standstill agreement between the Company and other parties
entered into prior to the date hereof in connection with the process conducted
by the Company to solicit acquisition proposals for the Company.

         Section 6.4 Disclosure of Certain Matters; Delivery of Certain Filings.
(a) The Company shall give prompt notice to Parent, and Parent or Sub shall give
prompt notice to the Company, of (i) any representation or warranty made by it
contained in this Agreement becoming untrue or inaccurate in any material
respect and (ii) the failure by it to comply with or satisfy in any material
respect any covenant, condition or agreement to be complied with or satisfied by
it under this Agreement; provided, however, that no such notification shall
affect the representations, warranties, covenants or agreements of the parties
or the conditions to the obligations of the parties under this Agreement.

                                      -30-
   35

                  (b) The Company shall give prompt notice to Parent, and Parent
or Sub shall give prompt notice to the Company, of: (i) any material notice or
other communication from any Person alleging that the consent of such Person is
or may be required in connection with the transactions contemplated by this
Agreement; (ii) any material notice or other communication from any Governmental
Entity in connection with the transactions contemplated by this Agreement; and
(iii) any actions, suits, claims, investigations or proceedings commenced or, to
the best of its knowledge threatened against, relating to or involving or
otherwise affecting it or any of its Subsidiaries which, if pending on the date
of this Agreement would have been required to have been disclosed pursuant to
Article IV or Article V or which relate to the consummation of the transactions
contemplated by this Agreement.

                  (c) The Company shall promptly advise Parent orally and in
writing if there occurs, to the Knowledge of the Company, any change or event
which results in the executive officers of the Company having a good faith
belief that such change or event has resulted in or is reasonably likely to
result in a Material Adverse Effect on the Company. Parent shall promptly advise
the Company orally and in writing if there occurs, to the Knowledge of Parent,
any change or event which results in the executive officers of Parent having a
good faith belief that such change or event has resulted in or is reasonably
likely to result in a Material Adverse Effect on Parent. The Company shall
provide to Parent, and Parent shall provide to the Company, copies of all
filings made by the Company or Parent, as the case may be, with any Governmental
Entity in connection with this Agreement and the transactions contemplated
hereby.

         Section 6.5 Conduct of Business of Sub Pending the Merger. During the
period from the date of this Agreement through the Effective Time, Sub shall not
engage in any activity of any nature except as provided in or contemplated by
this Agreement.

         Section 6.6 Modifications to Recommendations. Except as expressly
permitted by this Section 6.6, neither the Board of Directors of the Company nor
any committee thereof shall (i) withdraw, qualify, modify or amend, in a manner
adverse to Parent, the Recommendations or make any public statement, filing or
release inconsistent with such Recommendations (provided, however, that
following the Board of Directors' consideration and evaluation of an Acquisition
Proposal, it is understood that for the purposes hereof, if the Company adopts a
neutral position or no position with respect to the Acquisition Proposal, it
shall be considered an adverse modification of the Recommendations), (ii)
approve or recommend, or propose publicly to approve or recommend, any
Acquisition Proposal or (iii) cause the Company to enter into any acquisition
agreement or other similar agreement related to any Acquisition Proposal (each,
a "Subsequent Determination"), provided that if prior to the consummation of the
Offer the Board of Directors of the Company determines in good faith (after it
has received a Superior Proposal and after receipt of advice from outside
counsel) that the failure to make a Subsequent Determination would result in a
breach by the Board of Directors of the Company of its fiduciary duties to the
Company's stockholders under applicable law, the Board of Directors of the
Company may (subject to this and the following sentences) inform the Company's
stockholders that it no longer believes that the Offer and the Merger and the
other transactions contemplated hereby are advisable, but only at a time that is
72 hours following delivery by the Company to Parent of a written notice (a
"Subsequent Determination Notice") (i) advising Parent that the Board of
Directors of the Company has received a Superior Proposal, (ii) specifying the
terms and conditions of such Superior Proposal, including the amount per share
the Company's

                                      -31-
   36

stockholders will receive per Share (valuing any non-cash consideration at what
the Board of Directors of the Company determines in good faith, after
consultation with its independent financial advisor, to be the fair value of the
non-cash consideration) and including a copy thereof with all accompanying
documentation, (iii) identifying the person making such Superior Proposal and
(iv) stating that the Company intends to make a Subsequent Determination. After
providing such notice, the Company shall provide a reasonable opportunity to
Parent to make such adjustments in the terms and conditions of this Agreement as
would enable the Company to proceed with its Recommendations to its stockholders
without a Subsequent Determination; provided, however, that any such adjustment
to this Agreement shall be at the discretion of Parent at the time.

                                   ARTICLE VII
                              ADDITIONAL AGREEMENTS

         Section 7.1 Employee Benefits. (a) Parent shall take all necessary
action so that each person who is an employee of the Company or any of its
Subsidiaries immediately prior to the consummation of the Merger (including each
such person who is on vacation, temporary layoff, approved leave of absence,
sick leave or short- or long-term disability) (a "Retained Employee") shall
remain an employee of the Company or the Surviving Corporation or a Subsidiary
of the Company or of the Surviving Corporation, as the case may be, immediately
following the consummation of the Merger. Parent shall take all necessary action
so that each Retained Employee shall after the consummation of the Offer
continue to be credited with the unused vacation and sick leave credited to such
employee through the consummation of the Offer under the applicable vacation and
sick leave policies of the Company and its Subsidiaries, and Parent shall permit
or cause the Company, the Surviving Corporation and their Subsidiaries to permit
such employees to use such vacation and sick leave. Parent shall take all
necessary action so that, for purposes of eligibility and vesting service under
each employee benefit plan and determination of benefits under each paid time
off, vacation, severance, short-term disability and service award plans
maintained by Parent or any of its Subsidiaries in which employees or former
employees of the Company and its Subsidiaries become eligible to participate
upon or after the consummation of the Offer, each such person shall be given
credit for all service with the Company and its Subsidiaries (or all service
credited by the Company or its Subsidiaries) to the same extent as if rendered
to Parent or any of its Subsidiaries.

                  (b) Except as otherwise provided in this Section, Section 7.2
or Section 7.12, nothing in this Agreement shall be interpreted as limiting the
power of the Surviving Corporation to amend or terminate any particular Benefit
Plan or any other particular employee benefit plan, program, agreement or policy
or as requiring the Surviving Corporation to offer to continue (other than as
required by its terms) any written employment contract, subject to the terms and
conditions of the applicable plan, program, agreement or policies.

                  (c) Parent shall honor or cause to be honored by the Company,
the Surviving Corporation and their Subsidiaries all employment agreements,
bonus agreements, severance agreements, severance plans and non-competition
agreements with the persons who are directors, officers and employees of the
Company and its Subsidiaries (it being understood that nothing herein shall be
deemed to mean that the Company, the Surviving Corporation and their
Subsidiaries shall not be required to honor any of their obligations under any
such agreement).

                                      -32-
   37

                  (d) Parent shall, or shall cause the Company and the Surviving
Corporation to, (i) waive all limitations as to preexisting conditions,
exclusions and waiting periods with respect to participation and coverage
requirements applicable to the Retained Employees and former employees of the
Company and its Subsidiaries under any welfare or fringe benefit plan in which
such employees and former employees may be eligible to participate after the
consummation of the Offer, other than limitations or waiting periods that are in
effect with respect to such employees and that have not been satisfied under the
corresponding welfare or fringe benefit plan maintained by the Company for the
Retained Employees and former employees prior to the consummation of the Offer,
and (ii) provide each Retained Employee and former employee with credit under
any welfare plans in which such employee or former employee becomes eligible to
participate after the consummation of the Offer for any co-payments and
deductibles paid by such Retained Employee or former employee for the then
current plan year under the corresponding welfare plans maintained by the
Company prior to the consummation of the Offer.

         Section 7.2 Options.

                  (a) Except as set forth in Section 7.2(f), each Company Stock
Option that is outstanding immediately prior to the date the Offer is
consummated (the "Offer Consummation Date") pursuant to any Company Stock Plan
shall vest and become immediately exercisable at the time of the consummation of
the Offer. On the Offer Consummation Date with respect to Company Stock Options
held by persons who are not subject to the reporting requirements of Section
16(a) of the Exchange Act, and at the Effective Time with respect to Company
Stock Options held by persons who are subject to the reporting requirements of
Section 16(a) of the Exchange Act, each Company Stock Option shall be adjusted
to represent an option to purchase the number of shares of Company Common Stock
(a "Company Adjusted Option") (rounded down to the nearest full share)
determined by multiplying (i) the number of shares of Company Common Stock
subject to such Company Stock Option immediately prior to the Offer Consummation
Date with respect to Company Stock Options held by persons who are not subject
to the reporting requirements of Section 16(a) of the Exchange Act and
immediately prior to the Effective Time with respect to Company Stock Options
held by persons who are subject to the reporting requirements of Section 16(a)
of the Exchange Act, by (ii) 0.5, at an exercise price per share of Company
Common Stock equal to the exercise price per share of Company Common Stock
immediately prior to the Offer Consummation Date. In addition, promptly
following the Offer Consummation Date with respect to holders of Company Stock
Options who are not subject to the reporting requirements of Section 16(a) of
the Exchange Act, and promptly following the Effective Time with respect to
holders of Company Stock Options who are subject to the reporting requirements
of Section 16(a) of the Exchange Act, Parent shall pay to the holder of each
Company Stock Option an amount of cash (rounded up to the nearest cent) equal to
the product of (A) (x) $73.00 minus (y) the exercise price per share of Company
Common Stock immediately prior to the Offer Consummation Date and (B) the number
of shares of Company Common Stock subject to such option multiplied by 0.5
(rounded up to the nearest full share). Each Company Adjusted Option shall be
exercisable upon the same terms and conditions as under the applicable Company
Stock Plan and the applicable option agreement issued thereunder, except as
otherwise provided in this Section 7.2.

                  (b) At the Effective Time, each Company Adjusted Option shall
be assumed by Parent and become and represent an option to purchase the number
of Parent Shares (a "Parent

                                      -33-
   38

Substitute Option") (rounded to the nearest full share, or if there shall not be
a nearest share, the next greater full share) determined by multiplying (i) the
number of shares of Company Common Stock subject to such Company Adjusted Option
immediately prior to the Effective Time by (ii) 1.767, at an exercise price per
Parent Share (rounded up to the nearest tenth of a cent) equal to (A) the
exercise price per share of Company Common Stock immediately prior to the
Effective Time divided by 1.767. Parent shall pay cash to holders of Parent
Substitute Options in lieu of issuing fractional Parent Shares upon the exercise
of Parent Substitute Options. Each Company Adjusted Option so converted shall be
exercisable upon the same terms and conditions as under the applicable Company
Stock Plan and the applicable option agreement issued thereunder, except as
otherwise provided in this Section 7.2. Parent shall (i) on or prior to the
Effective Time, reserve for issuance the number of Parent Shares that will
become subject to Parent Substitute Options pursuant to this Section 7.2(b),
(ii) from and after the Effective Time, upon exercise of the Parent Substitute
Options in accordance with the terms thereof, make available for issuance all
Parent Shares covered thereby, (iii) at the Effective Time, assume the Company
Stock Plans, with the result that all obligations of the Company under the
Company Stock Plans, including with respect to Company Adjusted Options
outstanding at the Effective Time, shall be obligations of Parent following the
Effective Time, and (iv) as promptly as practicable after the Effective Time,
issue to each holder of an outstanding Company Adjusted Option a document
evidencing the foregoing assumption by Parent.

                  (c) The parties shall take all actions so that the Company
Adjusted Options converted by Parent qualify following the Effective Time as
incentive stock options as defined in Section 422 of the Code to the extent
permitted under Section 422 of the Code and to the extent the Company Adjusted
Options qualified as incentive stock options prior to the Effective Time;
provided, however, that nothing in this Section 7.2(c) shall prevent the
acceleration of the vesting or exercisability of any Company Stock Option, as
provided in Section 7.2(a).

                  (d) Parent shall, as promptly as practicable but in any event
no later than three days after the Effective Time, file a registration statement
on Form S-8 or other applicable form under the Securities Act, covering the
Parent Shares issuable upon the exercise of Parent Substitute Options created
upon the assumption by Parent of Company Adjusted Options under Section 7.2(b),
and will maintain the effectiveness of such registration, and the current status
of the prospectus contained therein, until the exercise or expiration of such
Parent Substitute Options.

                  (e) The parties will cooperate to take all reasonable steps
necessary to give effect to this Section 7.2.

                  (f) Notwithstanding the terms of Section 7.2(a), to the extent
an option holder holds any unexercisable incentive stock options ("Unvested
ISO") on the Offer Consummation Date that do not become exercisable upon the
consummation of the Offer pursuant to the terms of the Company Stock Plan(s)
under which such Unvested ISOs were granted, then, to the extent possible, each
such Unvested ISO shall be converted into the right to receive cash in full and
the other options held by such option holder shall be appropriately adjusted
such that the aggregate amount of cash payable to such option holder pursuant to
Section 7.2(a) and this Section 7.2(f) does not exceed the amount that would
otherwise be payable pursuant to Section 7.2(a).

                                      -34-
   39

         Section 7.3 Shareholder Approval; Preparation of Form S-4 and Proxy
Statement/Prospectus. (a) Parent and the Company shall, as soon as practicable
following the acceptance of Shares pursuant to the Offer, prepare and the
Company shall file with the SEC the Proxy Statement and Parent and the Company
shall prepare and Parent shall file with the SEC a registration statement on
Form S-4 (the "Form S-4") for the offer and sale of the Parent Shares pursuant
to the Merger and in which the Proxy Statement will be included as a prospectus.
Each of the Company and Parent shall use all reasonable efforts to have the Form
S-4 declared effective under the Securities Act as promptly as practicable after
such filing. The Company will use all reasonable efforts to cause the Proxy
Statement to be mailed to the Company's stockholders as promptly as practicable
after the Form S-4 is declared effective under the Securities Act. Parent shall
also take any action (other than qualifying to do business in any jurisdiction
in which it is not now so qualified or to file a general consent to service of
process) required to be taken under any applicable state securities laws in
connection with the issuance of Parent Shares in the Merger and the Company
shall furnish all information concerning the Company and the holders of capital
stock of the Company as may be reasonably requested in connection with any such
action and the preparation, filing and distribution of the Proxy Statement. No
filing of, or amendment or supplement to, or correspondence to the SEC or its
staff with respect to, the Form S-4 will be made by Parent, or the Proxy
Statement will be made by the Company, without providing the other party a
reasonable opportunity to review and comment thereon. Parent will advise the
Company, promptly after it receives notice thereof, of the time when the Form
S-4 has become effective or any supplement or amendment has been filed, the
issuance of any stop order, the suspension of the qualification of the Parent
Shares issuable in connection with the Merger for offering or sale in any
jurisdiction, or any request by the SEC for amendment of the Form S-4 or
comments thereon and responses thereto or requests by the SEC for additional
information. The Company will advise Parent, promptly after it receives notice
thereof, of any request by the SEC for the amendment of the Proxy Statement or
comments thereon and responses thereto or requests by the SEC for additional
information. If at any time prior to the Effective Time any information relating
to the Company or Parent, or any of their respective affiliates, officers or
directors, should be discovered by the Company or Parent which should be set
forth in an amendment or supplement to either of the Form S-4 or the Proxy
Statement, so that any of such documents would not include any misstatement of a
material fact or omit to state any material fact necessary to make the
statements therein, in light of the circumstances under which they were made,
not misleading, the party which discovers such information shall promptly notify
the other parties hereto and an appropriate amendment or supplement describing
such information shall be promptly filed with the SEC and, to the extent
required by law, disseminated to the stockholders of the Company.

                  (b) The Company shall establish, prior to or as soon as
practicable following the date upon which the Form S-4 becomes effective, a
record date (which shall be prior to or as soon as practicable following the
date upon which the Form S-4 becomes effective) for, duly call, give notice of,
convene and hold a meeting of its stockholders (the "Company Stockholders
Meeting") for the purpose of considering and taking action upon this Agreement
and the Merger and (with the consent of Parent) such other matters as may in the
reasonable judgment of the Company be appropriate for consideration at the
Company Stockholders Meeting. Once the Company Stockholders Meeting has been
called and noticed, the Company shall not postpone or

                                      -35-
   40

adjourn the Company Stockholders Meeting (other than for the absence of a
quorum) without the consent of Parent. Subject to its fiduciary duties under
applicable law, the Board of Directors of the Company shall include the
Recommendations in the Form S-4 and the Proxy Statement as such Recommendations
pertain to the Merger and this Agreement. The Company shall use its reasonable
best efforts to solicit from stockholders of the Company proxies for use at the
Company Stockholders Meeting and in favor of this Agreement and the Merger and
shall take all other actions reasonably necessary or advisable to secure the
vote or consent of stockholders required by the DGCL to effect the Merger.

                  (c) Parent agrees to cause all Shares owned by Parent or any
Subsidiary of Parent to be voted in favor of the Merger.

         Section 7.4 Access to Information. Upon reasonable notice and subject
to the terms of the Confidentiality Agreement, each of Company and Parent shall,
and shall cause each of its respective Subsidiaries to, afford to the other
party, and its respective Representatives all reasonable access, during normal
business hours during the period prior to the Effective Time, to all their
respective properties, books, contracts, commitments, records and
Representatives, during such period, each of Company and Parent shall (and shall
cause each of its respective Subsidiaries to) make available to the other party
(a) a copy of each report, schedule, registration statement and other document
filed or received by it during such period pursuant to the requirements of the
Federal or state securities laws or the Federal tax laws and (b) all other
information concerning its business, properties and personnel as the other party
may reasonably request. In the event of a termination of this Agreement for any
reason, each party shall promptly return or destroy, or cause to be returned or
destroyed, all nonpublic information so obtained from the other party or any of
its Subsidiaries.

         Section 7.5 Fees and Expenses. (a) If the Offer has not been accepted,
the Company agrees to pay Parent a fee equal to $75.5 million as a result of the
occurrence of any of the events set forth below (a "Trigger Event"):

                           (i) the Company shall have received an Acquisition
                  Proposal (other than the cash tender offer by SRM Acquisition
                  Corp (an affiliate of Shell Oil Company), pursuant to its
                  Offer to Purchase dated March 12, 2001, as amended to the date
                  of this Agreement, at a purchase price of $60 per Share (the
                  "Shell Tender Offer"), it being understood that the Company
                  shall be deemed to have received an Acquisition Proposal (x)
                  if SRM Acquisition Corp amends its tender offer by increasing
                  its tender offer price above $60 per Share (including cash,
                  securities or any combination thereof offered for Shares)
                  after the date of the Agreement, or (y) if an Acquisition
                  Proposal other than the Shell Tender Offer is made by any
                  other affiliate of Shell Oil Company) after the date of this
                  Agreement (but prior to the termination hereof), and at any
                  time prior to, or within 12 months after, the termination of
                  this Agreement (unless this Agreement is terminated pursuant
                  to Section 9.1(a), Section 9.1(b)(iv) or Section 9.1(e)), the
                  Company shall have entered into, or shall have publicly
                  announced its intention to enter into, an agreement or an
                  agreement in principle with respect to any Acquisition
                  Proposal;

                                      -36-
   41

                           (ii) the Company has provided Parent with a
                  Subsequent Determination Notice or the Board of Directors of
                  the Company (or any committee thereof) (A) shall have made a
                  Subsequent Determination, (B) shall include in the Schedule
                  14D-9 its Recommendations with modification or qualification
                  in a manner adverse to Parent, or (C) shall have resolved to,
                  or publicly announced an intention to, take any of the actions
                  as specified in this Section 7.5(a)(ii); or

                           (iii) (A) as of the final expiration date of the
                  Offer, all conditions to the consummation of the Offer shall
                  have been met or waived except for satisfaction of the Minimum
                  Condition, (B) there shall have been made subsequent to the
                  date of this Agreement (but before such expiration date of the
                  Offer) an Acquisition Proposal (other than the cash tender
                  offer by SRM Acquisition Corp (an affiliate of Shell Oil
                  Company), pursuant to the Shell Tender Offer, it being
                  understood that the Company shall be deemed to have received
                  an Acquisition Proposal (x) if SRM Acquisition Corp amends its
                  tender offer by increasing its tender offer price above $60
                  per Share (including cash, securities or any combination
                  thereof offered for Shares) after the date of the Agreement,
                  or (y) if an Acquisition Proposal other than the Shell Tender
                  Offer is made by any other affiliate of Shell Oil Company) and
                  (C) at any time prior to, or within 12 months after, the
                  expiration or termination of the Offer, the Company shall have
                  entered into, or shall have publicly announced its intention
                  to enter into, an agreement or agreements in principle with
                  respect to any Acquisition Proposal.

                  Any fee due under Section 7.5(a) shall be payable by wire
transfer of same day funds on (A) the date of termination of this Agreement if
this Agreement is terminated by the Company pursuant to Section 9.1(d), (B) the
date which is the third business date following the date of the termination of
this Agreement if this Agreement is terminated by Parent pursuant to Section
9.1(c) and (C) any fee due under clause (i) or (iii) above shall not be payable
until the Company shall have entered into, or shall have publicly announced its
intention to enter into an agreement or agreement in principle with respect to
any Acquisition Proposal.

                  (b) Except as set forth in this Section 7.5, all fees and
expenses incurred in connection with the Offer and the Merger, this Agreement
and the transactions contemplated by this Agreement shall be paid by the party
incurring such fees or expenses, whether or not the Offer or the Merger is
consummated; provided, that if this Agreement is terminated as a result of the
occurrence of a Trigger Event, in addition to any amounts paid or payable by the
Company to Parent pursuant to Section 7.5(a), the Company shall assume and pay,
or reimburse Parent for, all out-of-pocket fees payable and expenses reasonably
incurred by Parent (including the fees and expenses of its counsel) in
connection with this Agreement and the transactions contemplated hereby, up to a
maximum of $15 million.

                  (c) If the Company shall have breached or failed to perform in
any material respect any of its representations, warranties, covenants or other
agreements contained in this Agreement, which breach or failure to perform (A)
would give rise to the failure of a condition set forth in subclause (c) or (d)
of clause (3) of Exhibit A, and (B) is incapable of being or has not been cured
by the Company prior to or on the earlier of (x) the date which is 10 calendar
days immediately following written notice by Parent to the Company of such
breach or failure to

                                      -37-
   42

perform and (y) the expiration or termination of the Offer in accordance with
the terms of this Agreement, the Company shall assume and pay, or reimburse
Parent for, all out-of-pocket fees payable and expenses reasonably incurred by
Parent (including the fees and expenses of its counsel) in connection with this
Agreement and the transactions contemplated hereby, up to a maximum of $15
million.

                  (d) If the Company has terminated this Agreement pursuant to
Section 9.1(e) and such breach of a representation, warranty, covenant or other
agreement contained in this Agreement is incapable of being or has not been
cured by Parent prior to or on the date which is 10 calendar days immediately
following written notice by the Company to Parent of such breach or failure to
perform, Parent shall reimburse the Company for all out-of-pocket fees payable
and expenses reasonably incurred by the Company (including the fees and expenses
of its counsel) in connection with this Agreement and the transactions
contemplated hereby, up to a maximum of $15 million.

                  (e) Parent and the Company agree that the agreements contained
in Sections 7.5(a) and 7.5(b) hereof are an integral part of the transactions
contemplated by this Agreement and constitute liquidated damages and not a
penalty.

         Section 7.6 Public Announcements. Parent and the Company will consult
with each other before issuing any press release or otherwise making any public
statements with respect to the transactions contemplated by this Agreement and
shall not issue any such press release or make any such public statement prior
to such consultation, except as may be required by applicable law, or by
obligations pursuant to any listing agreement with any national securities
exchange.

         Section 7.7 Transfer Taxes. The Company and Parent shall cooperate in
the preparation, execution and filing of all returns, questionnaires,
applications or other documents regarding any real property transfer or gains,
sales, use, transfer, value added, stock transfer and stamp taxes, any transfer,
recording, registration and other fees and any similar taxes which become
payable in connection with the transactions contemplated by this Agreement
(together with any related interest, penalties or additions to tax, "Transfer
Taxes"). All Transfer Taxes shall be paid by the Company (without any
reimbursement whatsoever by Parent, its Subsidiaries or other affiliates) and
expressly shall not be a liability of any holder of Company Common Stock.

         Section 7.8 State Takeover Laws. If any "fair price" or "control share
acquisition" statute or other similar statute or regulation shall become
applicable to the transactions contemplated hereby, Parent and the Company and
their respective Boards of Directors shall use reasonable efforts to grant such
approvals and take such actions as are necessary so that the transactions
contemplated hereby may be consummated as promptly as practicable on the terms
contemplated hereby and otherwise act to minimize the effects of any such
statute or regulation on the transactions contemplated hereby.

         Section 7.9 Indemnification; Directors and Officers Insurance. (a)
Parent shall, or shall cause the Surviving Corporation to, honor for a period of
not less than six years from the Effective Time (or, in the case of matters
occurring at or prior to the Effective Time that have not

                                      -38-
   43

been resolved prior to the sixth anniversary of the Effective Time, until such
matters are finally resolved), all rights to indemnification or exculpation,
existing in favor of a director, officer, employee or agent (an "Indemnified
Person") of the Company or any of its Subsidiaries (including, without
limitation, rights relating to advancement of expenses and indemnification
rights to which such persons are entitled because they are serving as a
director, officer, agent or employee of another entity at the request of the
Company or any of its Subsidiaries), as provided in the Restated Certificate of
Incorporation of the Company, the Bylaws of the Company, in each case, as in
effect on the date of this Agreement, and relating to actions or events through
the Effective Time; provided, however, that the Surviving Corporation shall not
be required to indemnify any Indemnified Person in connection with any
proceeding (or portion thereof) to the extent involving any claim initiated by
such Indemnified Person unless the initiation of such proceeding (or portion
thereof) was authorized by the Board of Directors of the Company or unless such
proceeding is brought by an Indemnified Person to enforce rights under this
Section 7.9; provided further that any determination required to be made with
respect to whether an Indemnified Person's conduct complies with the standards
set forth under the DGCL, the Restated Certificate of Incorporation of the
Company, the Bylaws of the Company, as the case may be, shall be made by
independent legal counsel selected by such Indemnified Person and reasonably
acceptable to Parent; and provided further that nothing in this Section 7.9
shall impair any rights of any Indemnified Person. Without limiting the
generality of the preceding sentence, in the event that any Indemnified Person
becomes involved in any actual or threatened action, suit, claim, proceeding or
investigation after the Effective Time, Parent shall, or shall cause the
Surviving Corporation to, promptly advance to such Indemnified Person his or her
legal and other expenses (including the cost of any investigation and
preparation incurred in connection therewith), subject to the providing by such
Indemnified Person of an undertaking to reimburse all amounts so advanced in the
event of a non-appealable determination of a court of competent jurisdiction
that such Indemnified Person is not entitled thereto.

                  (b) Prior to the Effective Time and subject to the proviso in
the following sentence relating to the cost thereof, the Company shall have the
right to obtain and pay for in full a "tail" coverage directors' and officers'
liability insurance policy ("D&O Insurance") covering a period of not less than
six years after the Effective Time and providing coverage in amounts and on
terms consistent with the Company's existing D&O Insurance. In the event the
Company is unable to obtain such insurance, Parent shall cause the Surviving
Corporation to maintain the Company's D&O Insurance for a period of not less
than six years after the Effective Time; provided, that the Surviving
Corporation may substitute therefor policies of substantially similar coverage
and amounts containing terms no less advantageous to such former directors or
officers; provided further that if the existing D&O Insurance expires or is
cancelled during such period, Parent or the Surviving Corporation shall use its
best efforts to obtain substantially similar D&O Insurance; and provided further
that the Company shall not, without Parent's consent, expend an amount in excess
of 300% of the last annual premium paid prior to the date hereof to procure the
above described "tail" coverage and neither Parent nor the Surviving Corporation
shall be required to expend, in order to maintain or procure an annual D&O
Insurance policy, in lieu of a tail policy, an amount in excess of 300% of the
last annual premium paid prior to the date hereof, but in such case shall
purchase as much coverage as possible for such amount.

                                      -39-
   44

                  (c) The provisions of this Section 7.9 are intended to be for
the benefit of, and shall be enforceable by, each Indemnified Person, his or her
heirs and his or her personal representatives and shall be binding on all
successors and assigns of Parent, the Company and the Surviving Corporation.

         Section 7.10 Board of Directors. Promptly after such time as Sub
purchases Shares pursuant to the Offer (but subject to the satisfaction of the
Minimum Condition), Sub shall be entitled, to the fullest extent permitted by
law, to designate at its option up to that number of directors, rounded to the
nearest whole number, of the Company's Board of Directors, subject to compliance
with Section 14(f) of the Exchange Act, as will make the percentage of the
Company's directors designated by Sub equal to the aggregate voting power of the
shares of Common Stock held by Parent or any of its Subsidiaries; provided,
however, that in the event that Sub's designees are elected to the Board of
Directors of the Company, until the Effective Time, such Board of Directors
shall have at least two directors who are directors on the date of this
Agreement and who are not officers of the Company (the "Independent Directors");
and provided, further that, in such event, if the number of Independent
Directors shall be reduced below two for any reason whatsoever, the remaining
Independent Directors shall, to the fullest extent permitted by law, designate a
person to fill such vacancy who shall be deemed to be an Independent Director
for purposes of this Agreement or, if no Independent Directors then remain, the
other directors shall designate two persons to fill such vacancies who shall not
be officers or affiliates of the Company or any of its Subsidiaries, or officers
or affiliates of Parent or any of its Subsidiaries, and such persons shall be
deemed to be Independent Directors for purposes of this Agreement. Following the
election or appointment of Sub's designees pursuant to this Section 7.10 and
prior to the Effective Time, (A) any amendment, or waiver of any term or
condition, of this Agreement or the Restated Certificate of Incorporation or
Bylaws of the Company and (B) any termination of this Agreement by the Company,
any extension by the Company of the time for the performance of any of the
obligations or other acts of Sub or waiver or assertion of any of the Company's
rights hereunder, and any other consent or action by the Board of Directors with
respect to this Agreement, will require the concurrence of a majority of the
Independent Directors and no other action by the Company, including any action
by any other director of the Company, shall be required for purposes of this
Agreement. To the fullest extent permitted by applicable law, the Company shall
take all actions requested by Parent which are reasonably necessary to effect
the election of any such designee, including mailing to its stockholders the
Information Statement containing the information required by Section 14(f) of
the Exchange Act and Rule 14f-1 promulgated thereunder, and the Company agrees
to make such mailing with the mailing of the Schedule 14D-9 (provided that Sub
shall have provided to the Company on a timely basis all information required to
be included in the Information Statement with respect to Sub's designees).
Parent and Sub will be solely responsible for any information with respect to
either of them and their nominees, officers, directors and affiliates required
by Section 14(f) of the Exchange Act and Rule 14f-1 promulgated thereunder. In
connection with the foregoing, the Company will promptly, at the option of
Parent, to the fullest extent permitted by law, either increase the size of the
Company's Board of Directors and/or obtain the resignation of such number of its
current directors as is necessary to enable Sub's designees to be elected or
appointed to the Company's Board of Directors as provided above.

         Section 7.11 HSR Act Filings; Reasonable Best Efforts. (a) Each of
Parent and the Company shall (i) promptly make or cause to be made the filings
required of such party or any of

                                      -40-
   45

its Subsidiaries under the HSR Act and any other Antitrust Laws with respect to
the Offer, the Merger and the other transactions contemplated by this Agreement,
(ii) comply at the earliest practicable date with any request under the HSR Act
or such other Antitrust Laws for additional information, documents, or other
material received by such party or any of its Subsidiaries from the Federal
Trade Commission or the Department of Justice or any other Governmental Entity
in respect of such filings, the Offer, the Merger or such other transactions,
and (iii) cooperate with the other party in connection with any such filing and
in connection with resolving any investigation or other inquiry of any such
agency or other Governmental Entity under any Antitrust Laws with respect to any
such filing, the Offer, the Merger or such other transactions. Each of Parent
and the Company shall promptly inform the other of any communication with, and
any proposed understanding, undertaking, or agreement with, any Governmental
Entity regarding any such filings, the Offer, the Merger or such other
transactions.

                  (b) Each of Parent and the Company shall use all reasonable
best efforts to resolve such objections, if any, as may be asserted by any
Governmental Entity with respect to the Offer, the Merger or any other
transactions provided for in this Agreement under the Antitrust Laws. In
connection therewith, if any administrative or judicial action or proceeding is
instituted (or threatened to be instituted) challenging the Offer, the Merger or
any other transactions provided for in this Agreement as violative of any
Antitrust Law, each of Parent and the Company shall cooperate and use all
reasonable best efforts vigorously to contest and resist any such action or
proceeding and to have vacated, lifted, reversed, or overturned any decree,
judgment, injunction or other order, whether temporary, preliminary or
permanent, that is in effect and that prohibits, prevents, or restricts
consummation of the Offer, the Merger or any such other transactions. Each of
Parent and the Company shall use all reasonable best efforts to take such action
as may be required to cause the expiration of the notice periods under the HSR
Act or other Antitrust Laws with respect to the Offer, the Merger and such other
transactions as promptly as possible after the execution of this Agreement.

                  (c) Each of the parties agrees to use all reasonable best
efforts to take, or cause to be taken, all actions, and to do, or cause to be
done, and to assist and cooperate with the other parties in doing, all things
necessary, proper or advisable to consummate and make effective, in the most
expeditious manner practicable, the Offer, the Merger, and the other
transactions contemplated by this Agreement, including (i) the obtaining of all
other necessary actions or nonactions, waivers, consents and approvals from
Governmental Entities and the making of all other necessary registrations and
filings (including other filings with Governmental Entities, if any), (ii) the
obtaining of all necessary consents, approvals or waivers from third parties,
(iii) the preparation of the Form S-4, the Offer Documents, the Schedule 14D-9
and the Proxy Statement, and (iv) the execution and delivery of any additional
instruments necessary to consummate the transactions contemplated by, and to
fully carry out the purposes of, this Agreement, in each case subject to the
Company Board of Directors' fiduciary duties under applicable law.

                  (d) Notwithstanding anything to the contrary in this Section
7.11, (i) neither Parent nor any of its Subsidiaries shall be required to divest
any of their respective businesses, product lines or assets that could
reasonably be expected to have a Material Adverse Effect on Parent, (ii) neither
Parent nor any of its Subsidiaries shall be required to take or agree to take
any other action or agree to any limitation that could reasonably be expected to
have a Material Adverse Effect on Parent, (iii) neither the Company nor its
Subsidiaries shall be required to

                                      -41-
   46

divest any of their respective businesses, product lines or assets, or to take
or agree to take any other action or agree to any limitation that could
reasonably be expected to have a Material Adverse Effect on the Company, and
(iv) neither Parent nor Sub shall be required to waive any of the conditions to
the Offer set forth in Exhibit A or any of the conditions of to the Merger set
forth in Article VIII.

         Section 7.12 Stay Bonuses; Severance. (a) Prior to the Effective Time,
the Company shall be permitted to award bonuses to employees of the Company or
any of its Subsidiaries in an aggregate amount not to exceed $2,000,000, with
such bonuses to be allocated at the direction of its Chief Executive Officer
with the consent of Parent, which consent shall not be unreasonably withheld or
delayed. Such bonuses shall be paid upon the earlier of 90 days following the
Effective Time and 30 days following the date of termination hereof as described
in Article IX (the "Payment Date") to each employee to whom such a bonus has
been awarded and who continues to be employed by the Company (or any successor
or affiliate of the Company) on the Payment Date or whose employment terminates
prior to the Payment Date due to death, Disability, termination by the Company
(or any successor or affiliate of the Company) without Cause, or termination by
the employee with Good Reason (as such capitalized terms are defined in the
Company's Severance Protection Plan); provided, however, that no such bonus
shall be paid to any employee who has entered into a Severance Protection
Agreement with the Company and whose employment terminates prior to the Payment
Date entitling such employee to a severance payment pursuant to Section 3.1(b)
of such Severance Protection Agreement.

                  (b) Subject to Section 7.1(c), Parent shall maintain or cause
the Company or Surviving Corporation to maintain each of the Company's severance
policy as in effect on the date hereof as set forth in Item 7.12(b) of the
Company Letter or shall replace such policy with a policy providing equal or
more favorable compensation, for a period of at least two years from the
Effective Time.

                  (c) Each employee of the Company or any of its Subsidiaries
whose employment is terminated upon, or within 18 months following, the
consummation of the Offer, other than an employee who has entered into a
Severance Protection Agreement with the Company, shall receive a cash payment
from the Company or Parent in the amount of $8,000 which may, in the sole
discretion of such employee, be used to obtain outplacement services, to assist
in the transition to subsequent employment or for any other purpose.

         Section 7.13 Section 16 Matters. Prior to the Effective Time, Parent
and the Company shall take all such steps as may reasonably be required to cause
any dispositions of Shares (including derivative securities with respect to the
Shares) or acquisition of Parent Shares (including derivative securities with
respect to the Parent Shares) resulting from the transactions contemplated by
this Agreement by each individual who is subject to the reporting requirements
of Section 16(a) of the Exchange Act with respect to the Company to be exempt
under Rule 16b-3 promulgated under the Exchange Act, such steps to be taken in
accordance with the No-Action Letter, dated January 12, 1999, issued by the SEC
regarding such matters.

         Section 7.14 Tax Treatment. This Agreement is intended to constitute a
"plan of reorganization" with respect to the Offer and the Forward Merger for
United States Federal income tax purposes. From and after the date of this
Agreement, each party hereto shall use its

                                      -42-
   47

reasonable best efforts to cause the Offer and the Forward Merger to qualify,
and shall not, without the prior written consent of the other parties hereto,
knowingly take any actions or cause any actions to be taken which could
reasonably be expected to prevent the Offer and the Forward Merger from
qualifying as a reorganization under the provisions of Section 368(a) of the
Code. Following the Effective Time, neither the Surviving Corporation nor Parent
nor any of their respective affiliates shall take any action or cause any action
to be taken which could reasonably be expected to cause the Offer and the
Forward Merger to fail to qualify as a reorganization under Section 368(a) of
the Code. Parent shall use its reasonable best efforts to obtain an opinion of
Skadden, Arps, Slate, Meagher & Flom LLP (which includes its affiliated law
practice entities), or another nationally recognized United States Federal
income tax counsel or "Big Five" accounting firm ("Tax Counsel") (based on the
facts and customary representations and assumptions) that the Transaction will
be treated as a "reorganization" within the meaning of Section 368(a) of the
Code (the "Tax Opinion Standard"). Notwithstanding anything express or implied
to the contrary in this Agreement, but subject to the provisions of this Section
7.14, if such opinion cannot be obtained, then, in Parent's reasonable
discretion, the Reverse Merger shall be effected instead of the Forward Merger.

         Section 7.15 Affiliate Letters. As promptly as practicable, the Company
shall deliver to Parent a letter identifying all persons who are at the time
this Agreement is submitted for adoption by the stockholders of the Company,
"affiliates" of the Company for purposes of Rule 145 under the Securities Act.
The Company shall use all reasonable efforts to deliver or cause to be delivered
to Parent, prior to the expiration of the Offer, an Affiliate Letter in a
customary form for transactions of this type.

         Section 7.16 Litigation. The Company shall give Parent a reasonable
opportunity to participate in the defense of any litigation against the Company
and/or its directors relating to the transactions contemplated by this Agreement
or any other Acquisition Proposal and will not settle or compromise any such
action without the prior written consent of Parent, which consent shall not be
unreasonably withheld or delayed.

         Section 7.17 Rights Agreement. Except as expressly required by this
Agreement, the Company shall not, without the prior written consent of Parent,
amend the Rights Agreement or take any other action with respect to, or make any
determination under, the Rights Agreement, including a redemption of the Rights
or any action with respect to the Rights Agreement to facilitate an Acquisition
Proposal; provided, however, that the Company may amend or take appropriate
action under the Rights Agreement to delay the occurrence of a Distribution Date
(as defined in the Rights Agreement) in response to the public announcement of
an Acquisition Proposal.

         Section 7.18 Bank Debt. The Company agrees to use its reasonable best
efforts to seek the consent of its bank lenders and the issuers of letters of
credit to the Company to permit the consummation of the transactions
contemplated hereby, including, without limitation, the Offer and the Merger,
without necessity to repay the indebtedness of the Company to such lenders or to
replace such letters of credit.

                                      -43-
   48

                                  ARTICLE VIII
                              CONDITIONS PRECEDENT

         Section 8.1 Conditions to Each Party's Obligation to Effect the Merger.
The respective obligations of each party to effect the Merger shall be subject
to the fulfillment at or prior to the Effective Time of the following
conditions:

                  (a) Company Stockholder Approval. The Company Stockholder
Approval shall have been obtained; provided, however, that Parent and Sub shall
vote all of their shares of capital stock of the Company entitled to vote
thereon in favor of the Merger.

                  (b) No Injunction or Restraint. No statute, rule, regulation,
executive order, decree, temporary restraining order, preliminary or permanent
injunction or other order issued by any court of competent jurisdiction or other
Governmental Entity preventing the consummation of the Merger shall be in
effect; provided, however, that each of the parties shall have used their
reasonable best efforts to prevent the entry of any such temporary restraining
order, injunction or other order, including, without limitation, taking such
action as is required to comply with Section 7.11, and to appeal as promptly as
possible any injunction or other order that may be entered.

                  (c) Purchase of Shares. Sub shall have previously accepted for
payment and paid for Shares pursuant to the Offer; provided, however, that this
condition shall be deemed satisfied if Parent or Sub fails to accept for payment
and pay for Shares pursuant to the Offer in violation of the terms of this
Agreement and/or the Offer.

                  (d) Form S-4. The Form S-4 shall have become effective under
the Securities Act and shall not be the subject of any stop order or proceedings
seeking a stop order.

                  (e) Listing Parent Shares. The Parent Shares to be issued in
the Merger shall have been approved for listing on the NYSE.

                                   ARTICLE IX
                            TERMINATION AND AMENDMENT

         Section 9.1 Termination. This Agreement may be terminated at any time
prior to the Effective Time, whether before or after approval of this Agreement
and the Merger by the stockholders of the Company or Sub:

                  (a) by mutual written consent of Parent and the Company

                  (b) by either of Parent or the Company:

                           (i) if the Offer shall have expired or been
                  terminated in accordance with the terms of this Agreement
                  without Parent or Sub having accepted for payment any Shares
                  pursuant to the Offer, unless the failure to consummate the
                  Offer is the result of a willful and material breach of this
                  Agreement by the party seeking to terminate this Agreement;

                                      -44-
   49

                           (ii) if the Offer shall not have been consummated on
                  or before August 31, 2001 (the "Outside Date"), unless the
                  failure to consummate the Offer is the result of a willful and
                  material breach of this Agreement by the party seeking to
                  terminate this Agreement;

                           (iii) if the Merger shall not have been consummated
                  as a result of any condition thereto in Article VIII being
                  incapable of being satisfied; or

                           (iv) if any statute, rule, regulation, injunction or
                  decree having the effects set forth in subclause (a) or (b) of
                  clause (3) of Exhibit A shall be in effect and shall have
                  become final and nonappealable; or

                  (c) by Parent, upon the occurrence of the Trigger Event
described in Section 7.5(a)(ii) hereof;

                  (d) by the Company, if the Company makes a Subsequent
Determination in material compliance with Section 6.2 hereof and pursuant to the
provisions of Section 6.6 hereof, provided the Company has paid or concurrently
pays Parent the sums (including providing Parent with an undertaking confirming
the Company's obligation to reimburse expenses as required by Section 7.5)
required by Section 7.5(a) hereof; or

                  (e) by the Company (i) if Sub or Parent shall have breached in
any material respect any of their respective covenants, obligations or other
agreements under this Agreement, or (ii) if the representations and warranties
of Parent and Sub set forth in this Agreement that are qualified as to
materiality shall not be true and correct as of the date of the Agreement and as
of the expiration of the date of termination of this Agreement (except to the
extent expressly made as of an earlier date, in which case as of such date), or
any of the representations and warranties set forth in the Agreement that are
not so qualified by materiality shall not be true and correct in any material
respect as of the date of this Agreement and as of the date of termination of
this Agreement (except to the extent expressly made as of an earlier date, in
which case as of such date); provided that this right of termination shall not
be deemed to exist unless any such breaches of representation or warranty
(without regard to any "Materiality" or "Material Adverse Effect" or similar
qualifier or threshold), individually or in the aggregate, has had or could
reasonably be expected to have, a Material Adverse Effect on the Parent;
provided, further that the breach of the covenant, obligation, agreement,
representation or warranty is incapable of being or has not been cured by Parent
or Sub prior to or on the date which is 10 calendar days immediately following
written notice by the Company to Parent of such breach or failure to perform.

                  (f) by Parent (i) if the Company shall have breached in any
material respect any of its covenants, obligations or other agreements under
this Agreement, or (ii) if the representations and warranties of the Company set
forth in this Agreement that are qualified as to materiality shall not be true
and correct as of the date of the Agreement and as of the expiration of the date
of termination of this Agreement (except to the extent expressly made as of an
earlier date, in which case as of such date), or any of the representations and
warranties set forth in the Agreement that are not so qualified by materiality
shall not be true and correct in any material respect as of the date of this
Agreement and as of the date of termination of this Agreement

                                      -45-
   50

(except to the extent expressly made as of an earlier date, in which case as of
such date); provided that this right of termination shall not be deemed to exist
unless any such breaches of representation or warranty (without regard to any
"Materiality" or "Material Adverse Effect" or similar qualifier or threshold),
individually or in the aggregate, has had or could reasonably be expected to
have, a Material Adverse Effect on the Company; provided, further that the
breach of the covenant, obligation, agreement, representation or warranty is
incapable of being or has not been cured by the Company prior to or on the date
which is 10 calendar days immediately following written notice by Parent to the
Company of such breach or failure to perform.

         Section 9.2 Effect of Termination. In the event of a termination of
this Agreement by either the Company or Parent as provided in Section 9.1, this
Agreement shall forthwith become void and there shall be no liability or
obligation on the part of Parent, Sub or the Company or their respective
officers or directors, except with respect to Section 4.15, Section 5.16,
Section 7.5, this Section 9.2 and Article X and the last sentences of each of
Section 1.2(c) and Section 7.4; provided, however, that nothing herein shall
relieve any party for liability for any willful or knowing breach hereof.

         Section 9.3 Amendment. Subject to Section 1.1 and Section 7.10, this
Agreement may be amended by the parties hereto at any time before or after
obtaining the Company Stockholder Approval, but if the Company Stockholder
Approval shall have been obtained, thereafter no amendment shall be made which
by law requires further approval by the Company's stockholders without obtaining
such further approval. This Agreement may not be amended except by an instrument
in writing signed on behalf of each of the parties hereto.

         Section 9.4 Extension; Waiver. At any time prior to the Effective Time,
the parties hereto, by action taken or authorized by their respective Board of
Directors, may, to the extent legally allowed, (i) subject to the provisions of
Section 7.10, extend the time for the performance of any of the obligations or
other acts of the other parties hereto, (ii) subject to the provisions of
Section 7.10, waive any inaccuracies in the representations and warranties
contained herein or in any document delivered pursuant hereto or (iii) subject
to the provisions of Section 7.10, waive compliance with any of the agreements
or conditions contained herein. Any agreement on the part of a party hereto to
any such extension or waiver shall be valid only if set forth in a written
instrument signed on behalf of such party. The failure of any party to this
Agreement to assert any of its rights under this Agreement or otherwise shall
not constitute a waiver of those rights.

                                    ARTICLE X
                               GENERAL PROVISIONS

         Section 10.1 Non-Survival of Representations and Warranties and
Agreements. None of the representations and warranties in this Agreement or in
any instrument delivered pursuant to this Agreement shall survive the Effective
Time. This Section 10.1 shall not limit any covenant or agreement of the parties
which by its terms contemplates performance after the Effective Time of the
Merger.

         Section 10.2 Notices. All notices and other communications hereunder
shall be in writing and shall be deemed given if delivered personally,
telecopied (which is confirmed) or

                                      -46-
   51

sent by overnight courier (providing proof of delivery) to the parties at the
following addresses (or at such other address for a party as shall be specified
by like notice):

         (a) if to Parent or Sub, to:

                           The Williams Companies, Inc.
                           One Williams Center
                           Tulsa, Oklahoma 74172
                           Attn: William G. von Glahn and Rebecca H. Hilborne
                           Telecopy No.: (918) 573-5942

         with a copy to:

                           Skadden, Arps, Slate, Meagher & Flom LLP
                           Four Times Square
                           New York, NY 10036
                           Attn: Morris Kramer and Richard Grossman
                           Telecopy No.: 212-735-2000

         (b) if to the Company, to:

                           Barrett Resources Corporation
                           1515 Arapahoe Street
                           Tower 3, Suite 1000
                           Denver, Colorado 80202
                           Attn: Eugene A. Lang, Jr.
                           Telecopy No.: (303) 629-8275

         with copies to:

                           Sidley Austin Brown & Wood
                           Bank One Plaza
                           10 South Dearborn Street
                           Chicago, Illinois 60603
                           Attn: Thomas A. Cole and Paul L. Choi
                           Telecopy No.: (312) 853-7036

         Section 10.3 Interpretation; Definitions. When a reference is made in
this Agreement to an Article or a Section, such reference shall be to an Article
or a Section of this Agreement unless otherwise indicated. The table of contents
and headings contained in this Agreement are for reference purposes only and
shall not affect in any way the meaning or interpretation of this Agreement.
Whenever the words "include," "includes" or "including" are used in this
Agreement, they shall be deemed to be followed by the words "without
limitation."

         As used in this Agreement, the following terms have the meanings
specified or referred to in this Section 10.3 and shall be equally applicable to
both the singular and plural forms. Any agreement referred to below shall mean
such agreement as amended, supplemented or modified

                                      -47-
   52

from time to time to the extent permitted by the applicable provisions thereof
and by this Agreement.

         "ACQUISITION PROPOSAL" shall have the meaning set forth in Section
6.2(f).

         "AGREEMENT" means this Agreement and Plan of Merger, dated as of May 7,
2001, among Parent, Sub and the Company.

         "ANTITRUST LAWS" means, collectively, the HSR Act, the Sherman Act, as
amended, the Clayton Act, as amended, the Federal Trade Commission Act, as
amended, and any other Federal, state or foreign statutes, rules, regulations,
orders or decrees that are designed to prohibit, restrict or regulate actions
having the purpose or effect of monopolization or restraint of trade.

         "BENEFICIAL OWNER" or "BENEFICIALLY OWNING" shall have the meaning set
forth in Rule 13d-3 promulgated under the Exchange Act.

         "BENEFIT PLAN" means any collective bargaining agreement or any bonus,
pension, profit sharing, deferred compensation, incentive compensation, stock
ownership, stock purchase, stock option, phantom stock, retirement, vacation,
severance, disability, death benefit, hospitalization, medical, employee stock
purchase, stock appreciation, restricted stock or other employee benefit plan,
agreement or arrangement, in each case that is maintained, sponsored,
contributed to or required to be contributed to by the Company or any ERISA
Affiliate for the benefit of providing benefits to any current or former
employee, officer, director or consultant of the Company or any of its
Subsidiaries.

         "CERTIFICATE OF MERGER" shall have the meaning set forth in Section
2.3.

         "CERTIFICATES" shall have the meaning set forth in Section 3.2(b).

         "CLOSING DATE" shall have the meaning set forth in Section 2.2.

         "CODE" means the Internal Revenue Code of 1986, as amended.

         "COMPANY" shall have the meaning set forth in the introductory
paragraph of this Agreement.

         "COMPANY COMMON STOCK" shall have the meaning set forth in the second
recital provision of this Agreement.

         "COMPANY CONTRACTS" shall have the meaning set forth in Section
4.18(a).

         "COMPANY FILED SEC DOCUMENTS" shall have the meaning set forth in
Section 4.7.

         "COMPANY INTELLECTUAL PROPERTY" shall have the meaning set forth in
Section 4.20.

         "COMPANY LETTER" shall have the meaning set forth in Section 4.2.

         "COMPANY PREFERRED STOCK" shall have the meaning set forth in Section
4.3.

                                      -48-
   53

         "COMPANY RIGHTS" shall have the meaning set forth in Section 4.3.

         "COMPANY RIGHTS AGENT" shall have the meaning set forth in Section 4.3.

         "COMPANY RIGHTS AGREEMENT" shall have the meaning set forth in Section
4.3.

         "COMPANY SEC DOCUMENTS" shall have the meaning set forth in Section
4.6.

         "COMPANY SERIES A PREFERRED SHARES" shall have the meaning set forth in
Section 4.3.

         "COMPANY STOCK OPTIONS" shall have the meaning set forth in Section
4.3.

         "COMPANY STOCK PLANS" shall have the meaning set forth in Section 4.3.

         "COMPANY STOCKHOLDER APPROVAL" shall have the meaning set forth in
Section 4.16.

         "COMPANY STOCKHOLDERS MEETING" shall have the meaning set forth in
Section 6.2(b).

         "CONFIDENTIALITY AGREEMENT" shall have the meaning set forth in Section
7.4.

         "CONSENTS" means with respect to a Governmental Entity or Person, any
consent, approval, order or authorization of, or registration, declaration or
filing with or exemption by such Governmental Entity or Person, as the case may
be.

         "CONSTITUENT CORPORATIONS" shall have the meaning set forth in the
introductory paragraph of this Agreement.

         "CONSUMMATION OF THE OFFER" means the purchase of Shares pursuant to
the Offer.

         "DERIVATIVE TRANSACTIONS" shall have the meaning set forth in Section
4.22(b).

         "D&O INSURANCE" shall have the meaning set forth in Section 7.9(b).

         "DGCL" means the General Corporation Law of the State of Delaware.

         "EFFECTIVE TIME" shall have the meaning set forth in Section 2.3.

         "ENVIRONMENTAL LAWS" shall mean all foreign, Federal, state and local
laws, regulations, rules and ordinances relating to pollution or protection of
the environment or human health and safety, including, without limitation, laws
relating to releases or threatened releases of Hazardous Substances into the
indoor or outdoor environment (including, without limitation, ambient air,
surface water, groundwater, land, surface and subsurface strata) or otherwise
relating to the manufacture, processing, distribution, use, treatment, storage,
Release, transport or handling of Hazardous Substances; all laws and regulations
with regard to recordkeeping, notification, disclosure and reporting
requirements respecting Hazardous Substances; all laws relating to endangered or
threatened species of fish, wildlife and plants and the management or use of
natural resources; and common law to the extent it relates to or applies to
exposure to or impact of Hazardous Substances on persons or property.

                                      -49-
   54

         "ERISA" means the Employee Retirement Income Security Act of 1974, as
amended, together with the rules and regulations promulgated thereunder.

         "ERISA AFFILIATE" shall have the meaning set forth in Section 4.13(b).

         "ERISA BENEFIT PLAN" means a U.S. Benefit Plan maintained as of the
date of this Agreement which is also an "employee pension benefit plan" (as
defined in Section 3(2) of ERISA) or which is also an "employee welfare benefit
plan" (as defined in Section 3(1) of ERISA).

         "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended,
together with the rules and regulations promulgated thereunder.

         "EXCHANGE AGENT" shall have the meaning set forth in Section 3.2(a).

         "EXCHANGE FUND" shall have the meaning set forth in Section 3.2(a).

         "EXCHANGE RATIO" shall have the meaning set forth in the third recital
provision of this Agreement (subject to adjustment as contemplated by Section
3.4).

         "EXPENSES" means documented and reasonable out-of-pocket fees and
expenses incurred or paid by or on behalf of Parent in connection with the
Offer, the Merger or the consummation of any of the transactions contemplated by
this Agreement, including all reasonable fees and expenses of law firms,
commercial banks, investment banking firms, accountants, experts and consultants
to Parent.

         "FORM S-4" shall have the meaning set forth in Section 7.3.

         "FORWARD MERGER" shall have the meaning set forth in the second recital
provision of this Agreement.

         "GAAP" means United States generally accepted accounting principles.

         "GOLDMAN, SACHS" shall have the meaning set forth in Section 1.2(a).

         "GOVERNMENTAL ENTITY" means any Federal, state, local or foreign
government or any court, tribunal, administrative agency or commission or other
governmental or other regulatory authority or agency, domestic, foreign or
supranational.

         "HAZARDOUS SUBSTANCES" shall mean (a) any petrochemical or petroleum
products, radioactive materials, asbestos in any form that is or could become
friable, urea formaldehyde foam insulation, transformers or other equipment that
contain dielectric fluid containing polychlorinated biphenyls, and radon gas;
(b) any chemicals, materials or substances defined as or included in the
definition of "hazardous substances," "hazardous wastes," "hazardous materials,"
"restricted hazardous materials," "extremely hazardous substances," "toxic
substances," "contaminants" or "pollutants" or words of similar meaning and
regulatory effect; or (c) any other chemical, material or substance, exposure to
which is prohibited, limited, or regulated by any applicable Environmental Law.

                                      -50-
   55

         "HSR ACT" means the Hart-Scott-Rodino Antitrust Improvements Act of
1976, as amended.

         "INDEBTEDNESS" shall mean, with respect to any Person, without
duplication, (a) all obligations of such Person for borrowed money, (b) all
obligations of such Person evidenced by bonds, debentures, notes or similar
instruments, (c) all letters of credit issued for the account of such Person
(excluding letters of credit issued for the benefit of suppliers to support
accounts payable to suppliers incurred in the ordinary course of business), (d)
all capitalized lease obligations of such Person, (e) all obligations of such
Person under interest rate or currency swap transactions (valued at the
termination value thereof), and (f) all guarantees and arrangements having the
economic effect of a guarantee of such Person of any indebtedness of any other
Person.

         "INDEMNIFIED PERSON" shall have the meaning set forth in Section
7.9(a).

         "INDEPENDENT DIRECTORS" shall have the meaning set forth in Section
7.10.

         "INFORMATION STATEMENT" shall have the meaning set forth in Section
4.8.

         "KNOWLEDGE" shall mean the actual knowledge of the executive officers
of the Company or the executive officers of Parent, as the case may be.

         "LIENS" means any pledges, claims, liens, charges, encumbrances and
security interests of any kind or nature whatsoever.

         "MATERIAL ADVERSE CHANGE" or "MATERIAL ADVERSE EFFECT" means, when used
in connection with the Company or Parent, as the case may be, any change or
effect (or any development that, insofar as can reasonably be foreseen, is
likely to result in any change or effect) that is materially adverse to the
business, properties, assets, condition (financial or otherwise) or results of
operations of the Company and its Subsidiaries taken as a whole, or Parent and
its Subsidiaries taken as a whole, as the case may be, provided, however, that
(i) any adverse change, effect or development that is caused by or results from
conditions affecting the United States economy generally or the economy of any
nation or region in which the Company or Parent, as the case may be, or its
Subsidiaries conducts business that is material to the business of the Company
or Parent, as the case may be, and its Subsidiaries, taken as a whole, shall not
be taken into account in determining whether there has been (or whether there
could reasonably be foreseen) a "Material Adverse Change" or "Material Adverse
Effect" with respect to the Company or Parent, as the case may be, (ii) any
adverse change, effect or development that is caused by or results from
conditions generally affecting the industries (including the oil and gas
industry) in which the Company or Parent, as the case may be, conducts its
business shall not be taken into account in determining whether there has been
(or whether there could be reasonably be foreseen) a "Material Adverse Change"
or "Material Adverse Effect" with respect to the Company or Parent, as the case
may be, and (iii) any adverse change, effect or development that is caused by or
results from the announcement or pendency of this Agreement, the Offer, the
Merger or the transactions contemplated hereby shall not be taken into account
in determining whether there has been (or whether there could reasonably be
foreseen) a "Material

                                      -51-
   56

Adverse Change" or "Material Adverse Effect" with respect to the Company or
Parent, as the case may be.

         "MERGER" shall have the meaning set forth in Section 2.1.

         "MERGER CONSIDERATION" shall have the meaning set forth in the third
recital provision of this Agreement.

         "MINIMUM CONDITION" shall have the meaning set forth in Exhibit A of
this Agreement.

         "NYSE" means the New York Stock Exchange, Inc.

         "OFFER" shall have the meaning set forth in the second recital
provision of this Agreement.

         "OFFER CONDITIONS" shall have the meaning set forth in Section 1.1(a).

         "OFFER CONSIDERATION" shall have the meaning set forth in the second
recital provision of this Agreement.

         "OFFER DOCUMENTS" shall have the meaning set forth in Section 1.1(c).

         "OUTSIDE DATE" shall have the meaning set forth in Section 9.1(b).

         "PARENT" shall have the meaning set forth in the introductory paragraph
of this Agreement.

         "PARENT COMMON STOCK" shall have the meaning set forth in the third
recital provision of this Agreement.

         "PARENT FILED SEC DOCUMENTS" shall have the meaning set forth in
Section 5.7.

         "PARENT LETTER" means the letter from Parent to the Company dated the
date hereof, which letter relates to this Agreement and is designated therein as
the Parent Letter.

         "PARENT OPTIONS" shall have the meaning set forth in Section 7.2(b).

         "PARENT RIGHTS" means the rights to purchase Series A Junior
Participating Preferred Stock issued pursuant to the Parent Rights Agreement.

         "PARENT RIGHTS AGREEMENT" means the Rights Agreement, dated as of
February 6, 1996, between Parent and First Chicago Trust Company of New York, as
rights agent, as amended.

         "PARENT SEC DOCUMENTS" shall have the meaning set forth in Section 5.6.

         "PARENT SHARES" shall have the meaning set forth in the second recital
provision of this Agreement.

         "PARENT STOCK EQUIVALENTS" shall have the meaning set forth in Section
5.3.

                                      -52-
   57

         "PARENT STOCK OPTIONS" shall have the meaning set forth in Section 5.3.

         "PERMITS" means approvals, authorizations, certificates, filings,
franchises, licenses, notices, permits and rights.

          "PERSON" means an individual, corporation, partnership, limited
liability company, joint venture, association, trust, unincorporated
organization or other entity (including any person as defined in Section
13(d)(3) of the Exchange Act).

         "PETRIE PARKMAN" shall have the meaning set forth in Section 1.2(a).

         "PROXY STATEMENT" shall have the meaning set forth in Section 4.5(b).

         "RECOMMENDATIONS" shall have the meaning set forth Section 1.2.

         "REPRESENTATIVE" means with respect to any Person, its officers,
directors, investment bankers, attorneys, accountants, consultants or other
agents, advisors or representatives.

         "RETAINED EMPLOYEE" shall have the meaning set forth in Section 7.1(a).

         "REVERSE MERGER" shall have the meaning set forth in the fourth recital
provision of this Agreement.

         "RIGHTS AGREEMENT" shall mean that certain Rights Agreement between the
Company and BankBoston, N.A. dated August 5, 1997, as amended.

         "SCHEDULE 14D-9" shall have the meaning set forth in Section 1.2(b).

         "SCHEDULE TO" shall have the meaning set forth in Section 1.1(c).

         "SEC" means the Securities and Exchange Commission.

         "SECURITIES ACT" means the Securities Act of 1933, as amended, together
with the rules and regulations promulgated thereunder.

         "SHARES" shall have the meaning set forth in the second recital
provision of this Agreement.

         "SIGNIFICANT SUBSIDIARY" of any person means a Subsidiary of such
person that would constitute a "significant subsidiary" of such person within
the meaning of Rule 1.02(v) of Regulation S-X as promulgated by the SEC.

         "STOCK EQUIVALENTS" shall have the meaning set forth in Section 4.3.

         "SUB" shall have the meaning set forth in the introductory paragraph of
this Agreement.

         "SUBSEQUENT DETERMINATION" shall have the meaning set forth in Section
6.6.

         "SUBSEQUENT DETERMINATION NOTICE" shall have the meaning set forth in
Section 6.6.

                                      -53-
   58

         "SUBSIDIARY" or "SUBSIDIARY" of any person means another person, an
amount of the voting securities, other voting ownership or voting partnership
interests of which is sufficient to elect at least a majority of its Board of
Directors or other governing body (or, if there are no such voting interests,
50% or more of the equity interests of which) is owned directly or indirectly by
such first person.

         "SUPERIOR PROPOSAL" shall have the meaning set forth in Section 6.2(f).

         "SURVIVING CORPORATION" shall have the meaning set forth in Section
2.1.

         "TAX" and "TAXES" means any federal, state, local or foreign net
income, gross income, gross receipts, windfall profit, severance, property,
production, sales, use, license, excise, franchise, employment, payroll,
withholding, alternative or add-on minimum or any other tax, custom, duty, levy,
tariff, governmental fee or other like assessment or charge of any kind
whatsoever, together with any interest or penalty, addition to tax or additional
amount imposed by any Governmental Entity.

         "TAX OPINION STANDARD" shall have the meaning set forth in Section
7.14.

         "TAX RETURN" means any return, report or similar statement (including
any related or supporting information) required to be filed with respect to any
Tax including, without limitation, any information return, claim for refund,
amended return or declaration of estimated Tax.

         "TERMINATION FEE" shall have the meaning set forth in Section 7.5(b).

         "THIRD PARTY" means any Person (or group of Persons) other than Parent
and its affiliates.

         "TRANSACTION" shall have the meaning set forth in the eighth recital
provision of this Agreement.

         "TRANSFER TAXES" shall have the meaning set forth in Section 7.7.

         "TREASURY REGULATIONS" means the final and temporary (but not proposed)
income tax regulations promulgated under the Code, as such regulations may be
amended from time to time (including corresponding provisions of succeeding
regulations).

         "TRIGGER EVENT" shall have the meaning set forth in Section 7.5(a).

         Section 10.4 Counterparts. This Agreement may be executed in
counterparts, all of which shall be considered one and the same agreement, and
shall become effective when one or more counterparts have been signed by each of
the parties and delivered to the other parties, it being understood that all
parties need not sign the same counterpart.

         Section 10.5 Entire Agreement; No Third-Party Beneficiaries. Except for
the Confidentiality Agreement, this Agreement constitutes the entire agreement
and supersedes all prior agreements and understandings, both written and oral,
among the parties with respect to the

                                      -54-
   59

subject matter hereof. This Agreement, except for the provisions of Section 7.1,
Section 7.2, Section 7.9, Section 7.12 and Section 7.13, is not intended to
confer upon any person other than the parties hereto any rights or remedies
hereunder.

         Section 10.6 Governing Law. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of Delaware, regardless of
the laws that might otherwise govern under applicable principles of conflicts of
laws thereof.

         Section 10.7 Assignment. Neither this Agreement nor any of the rights,
interests or obligations hereunder shall be assigned by any of the parties
hereto (whether by operation of law or otherwise) without the prior written
consent of the other parties. Subject to the preceding sentence, this Agreement
shall be binding upon, inure to the benefit of, and be enforceable by, the
parties and their respective successors and assigns. Notwithstanding the
foregoing, Sub shall have the right, effective upon written notice to the
Company, to transfer or assign, in whole or from time to time in part, to Parent
or to one or more other wholly-owned Subsidiaries of Parent, the right to
purchase Shares tendered pursuant to the Offer, but any such transfer or
assignment shall in no way prejudice the rights of tendering stockholders to
receive payment for their Shares validly tendered and accepted for payment
pursuant to the Offer, adversely affect the ability of the parties to complete
the Transaction or relieve Sub of its obligations hereunder.

         Section 10.8 Severability. If any term or other provision of this
Agreement is invalid, illegal or incapable of being enforced by any rule of law,
or public policy, all other conditions and provisions of this Agreement shall
nevertheless remain in full force and effect so long as the economic and legal
substance of the transactions contemplated hereby are not affected in any manner
materially adverse to any party. Upon such determination that any term or other
provision is invalid, illegal or incapable of being enforced, the parties shall
negotiate in good faith to modify this Agreement so as to effect the original
intent of the parties as closely as possible in a mutually acceptable manner in
order that the transactions contemplated by this Agreement may be consummated as
originally contemplated to the fullest extent possible.

         Section 10.9 Enforcement of this Agreement. The parties hereto agree
that irreparable damage would occur in the event that any of the provisions of
this Agreement were not performed in accordance with their specific terms or
were otherwise breached. It is accordingly agreed that the parties shall be
entitled to an injunction or injunctions to prevent breaches of this Agreement
and to enforce specifically the terms and provisions hereof in any court of the
United States or any state having jurisdiction, such remedy being in addition to
any other remedy to which any party is entitled at law or in equity.

         Section 10.10 Obligations of Subsidiaries. Whenever this Agreement
requires any Subsidiary of Parent (including Sub) or of the Company to take any
action, such requirement shall be deemed to include an undertaking on the part
of Parent or the Company, as the case may be, to cause such Subsidiary to take
such action.

                                      -55-
   60

         IN WITNESS WHEREOF, Parent, Sub and the Company have caused this
Agreement to be signed by their respective officers thereunto duly authorized
all as of the date first written above.

                                   THE WILLIAMS COMPANIES, INC.

                                   By: /s/ Keith E. Bailey
                                       -----------------------------------------
                                            Name:  Keith E. Bailey
                                            Title: Chairman, President and Chief
                                                   Executive Officer

                                   RESOURCES ACQUISITION CORP.

                                   By: /s/ Steven J. Malcolm
                                       -----------------------------------------
                                            Name:  Steven J. Malcolm
                                            Title: President

                                   BARRETT RESOURCES CORPORATION

                                   By: /s/ Peter A. Dea
                                       -----------------------------------------
                                            Name:  Peter A. Dea
                                            Title: Chairman and Chief Executive
                                                   Officer

                                      -56-
   61

                                                                       EXHIBIT A

                             CONDITIONS OF THE OFFER

                  Notwithstanding any other provision of the Offer, subject to
the terms of the Agreement, Sub shall not be required to accept for payment or
pay for, (subject to any applicable rules and regulations of the SEC, including
Rule 14e-1(c) under the Exchange Act (relating to Sub's obligation to pay for or
return tendered Shares after the termination or withdrawal of the Offer)) any
Shares tendered, if by the expiration of the Offer (as it may be extended in
accordance with the requirements of Section 1.1), (1) there shall not have been
validly tendered and not withdrawn prior to the expiration of the Offer
16,730,502 shares of Company Common Stock (the "Minimum Condition"), (2) the
applicable waiting period under the HSR Act and any other applicable Antitrust
Laws shall not have expired or been terminated, or (3) at any time on or after
the date of the Agreement and prior to the acceptance for payment of Shares
pursuant to the Offer, any of the following conditions exist:

                  (a) there shall be instituted or pending any action or
proceeding by any Governmental Entity:

                           (i) challenging or seeking to make illegal, to delay
                  materially or otherwise directly or indirectly to restrain or
                  prohibit the making of the Offer or the Merger, the acceptance
                  for payment of, or the payment for, some of or all the Shares
                  by Parent or Sub or the consummation by Parent or Sub of the
                  Merger or seeking to obtain material damages,

                           (ii) seeking to restrain or prohibit Parent's or
                  Sub's ownership or operation (or that of their respective
                  Subsidiaries or affiliates) of all or any material portion of
                  the business or assets of the Company and its Subsidiaries,
                  taken as a whole, or of Parent and its Subsidiaries, taken as
                  a whole, or to compel Parent or any of its Subsidiaries or
                  affiliates to dispose of or hold separate all or any material
                  portion of the business or assets of the Company and its
                  Subsidiaries, taken as a whole, or of Parent and its
                  Subsidiaries, taken as a whole,

                           (iii) seeking to impose material limitations on the
                  ability of Parent or any of its Subsidiaries effectively to
                  exercise full rights of ownership of the Shares, including,
                  without limitation, the right to vote any Shares acquired or
                  owned by Parent or any of its Subsidiaries or affiliates on
                  all matters properly presented to the Company's stockholders,
                  or

                           (iv) seeking to require divestiture by Parent or any
                  of its Subsidiaries of any Shares; or

                  (b) there shall be any action taken, or any statute, rule,
regulation, injunction, order or decree enacted, enforced, promulgated, issued
or deemed applicable to the Agreement, the Offer or the Merger, by any
Governmental Entity that is reasonably likely, directly or indirectly, to result
in any of the consequences referred to in clauses (i) through (iv) of paragraph
(a) above, subject as aforesaid; or

                                       A-1
   62

                  (c) the Company shall have breached or failed to perform in
any material respect any of its covenants, obligations or agreements under the
Agreement; or

                  (d) the representations and warranties of the Company set
forth in the Agreement that are qualified as to materiality shall not be true
and correct as of the date of the Agreement and as of the expiration of the
Offer (including any extension thereof) (except to the extent expressly made as
of an earlier date, in which case as of such earlier date), or any of the
representations and warranties set forth in the Agreement that are not so
qualified as to materiality shall not be true and correct in any material
respect as of the date of the Agreement and as of the expiration of the Offer
(except to the extent expressly made as of an earlier date, in which case as of
such earlier date); provided that this condition shall not be deemed to exist
unless any such breaches of representation or warranty (without regard to any
"Materiality" or "Material Adverse Effect" or similar qualifier or threshold),
individually or in the aggregate, has had or could reasonably be expected to
have, a Material Adverse Effect on the Company; or

                  (e) this Agreement shall have been terminated in accordance
with its terms; or

                  (f) the Board of Directors of the Company (or any committee
thereof) shall have made a Subsequent Determination;

which, in the good faith judgment of Parent in any such case makes it
inadvisable to proceed with such acceptance for payment or payment.

                  The foregoing conditions are for the sole benefit of Parent
and Sub and may, subject to the terms of this Agreement, be waived by Parent and
Sub in their reasonable discretion in whole at any time or in part from time to
time. The failure by Parent or Sub at any time to exercise its rights under any
of the foregoing conditions shall not be deemed a waiver of any such right; the
waiver of any such right with respect to particular facts and circumstances
shall not be deemed a waiver with respect to any other facts and circumstances,
and each such right shall be deemed an ongoing right which may be asserted at
any time or from time to time. Terms used but not defined herein shall have the
meaning assigned to such terms in the Agreement to which this Exhibit A is a
part.

                                      A-2

   1
                                                                Exhibit (d) (2)

                                  March 9, 2001

Williams Companies, Inc.
One Williams Center, 49-1
Tulsa, OK  74172

Attention:  Mark Wilson

Ladies and Gentlemen:

                You have requested information regarding Barrett Resources
Corporation (the "Company") for the purposes of evaluating a possible business
combination involving the Company and you (a "Transaction"). It is understood
and agreed that this agreement creates no obligation to enter into any
Transaction or any agreement relating to a Transaction. To induce the Company to
furnish information to you, you hereby agree as follows:

                1.      As used herein:

                "Act" means the Securities Exchange Act of 1934, as amended;

                "Affiliate" means any Person that (i) directly or indirectly
        controls you, (ii) directly or indirectly is controlled by you or (iii)
        is under direct or indirect common control with you;

                "Information" means information regarding the Company or any of
        its subsidiaries or their respective assets or businesses which is
        furnished to you by the Company or its representatives;

                "Person" shall have the meaning contained in Section 3(a)(9) of
        the Act; and

                "Restricted Period" means the period commencing on the date
        hereof and ending on the close of business on May 11, 2001.

                2.      All Information will be kept confidential by you, except
that you may disclose or make available Information to your directors, officers
and employees and to representatives of your advisors for the exclusive purpose
of assisting you in the evaluation of a possible Transaction, all of whom shall
be specifically informed by you or your representatives of the confidential
character of such Information and that by receiving such information they are
agreeing to be bound by the terms of this agreement relating to the confidential
treatment of such Information. You will not use, or permit any of your
representatives to use, any of the Information for any purpose other than the
evaluation of a possible Transaction, and you will not make any Information
available to any Person for any other purpose whatsoever.

                3.      You hereby acknowledge that you are aware (and that
prior to the disclosure of any Information to any Person pursuant to paragraph 2
such Person will be advised)

   2

March 9, 2001
Page 2

that the United States securities laws prohibit any Person who has material
non-public information about a company from purchasing or selling securities of
such company or from communicating such information to any other Person under
circumstances in which it is reasonably foreseeable that such Person is likely
to purchase or sell such securities. In the event that you disclose any
Information to any Person, whether or not such disclosure is permitted under
paragraph 2, you shall be liable to the Company for any failure by such Person
to treat such Information in the same manner as you is obligated to treat such
Information under the terms of this agreement.

                4.      Unless specifically requested in writing in advance by
the Company, you will not at any time during the Restricted Period (and you will
not at any time during the Restricted Period assist or encourage others to):

                        (a)     acquire or agree, offer, seek or propose to
                acquire, directly or indirectly, alone or in concert with any
                other Person, by purchase or otherwise, any ownership,
                including, but not limited to, beneficial ownership as defined
                in Rule 13d-3 under the Act, of any of the assets, businesses or
                securities of the Company or any subsidiary thereof, or any
                rights or options to acquire such ownership (including from any
                third party);

                        (b)     solicit proxies or consents (as such terms are
                defined in Rule 14a-1 under the Act), whether or not such
                solicitation is exempt under Rule 14a-2 under the Act, with
                respect to any matter from holders of any shares of stock of the
                Company or any securities convertible into or exchangeable for
                or exercisable (whether currently or upon the occurrence of any
                contingency) for the purchase of such stock, or make any
                communication exempted from the definition of solicitation by
                Rule 14a-1(l)(2)(iv) under the Act;

                        (c)     initiate, or induce or attempt to induce any
                other Person, entity or group (as defined in Section 13(d)(3) of
                the Act) to initiate, any stockholder proposal, consent
                solicitation or tender offer for any securities of the Company
                or any subsidiary thereof, any change of control of the Company
                or any subsidiary thereof or the convening of a stockholders'
                meeting of the Company or any subsidiary thereof;

                        (d)     otherwise seek or propose to influence or
                control the management or policies of the Company or any
                subsidiary thereof;

                        (e)     enter into any discussions, negotiations,
                arrangements or understandings with any other Person with
                respect to any matter described in the foregoing subparagraphs
                (a) through (d);

                        (f)     take any action inconsistent with any of the
                foregoing subparagraphs (a) through (e); or

   3

March 9, 2001
Page 3

                        (g)     take any action not required by law with respect
                to any of the matters described in this paragraph 4 that
                requires public disclosure.

                5.      If at any time during the Restricted Period you are
approached by any Person concerning your or their participation in a transaction
involving any of the assets, businesses or securities of the Company or any
subsidiary thereof, you will promptly inform us of the nature of such contact
and the parties thereto.

                6.      Except with the Company's prior written approval, you
will not disclose, and you will not permit your representatives to disclose, to
any Person other than the Persons described in paragraph 2, the fact that you
are engaged in discussions with the Company regarding a Transaction (or are
participating in the Company's publicly announced process for soliciting
proposals for a possible Transaction), the fact that the Information has been
made available to you or that you have inspected any portion of the Information
or the fact that you are subject to any of the restrictions described in
paragraph 4; provided, however, that you may make such disclosure if you have
received the opinion of your outside counsel that such disclosure must be made
by you in order that you not commit a violation of law and, if the action which
is to be disclosed was in violation of paragraph 4, such disclosure expressly
states such violation.

                7.      In the event that you are requested in any proceeding to
disclose any Information received by you or any matter subject to paragraph 6,
you will give us prompt notice of such request so that we may seek an
appropriate protective order. If in the absence of a protective order you are
nonetheless compelled to disclose any such Information or matter, you may
disclose such Information or matter without liability hereunder, provided that
you give us written notice of the Information or matter to be disclosed as far
in advance of its disclosure as is practicable and uses its best efforts to
obtain assurances that confidential treatment will be accorded to such
Information or matter.

                8.      The restrictions with respect to Information set forth
in paragraph 2 shall not apply to any Information furnished to you by the
Company or its representatives which you demonstrate (i) is on the date hereof
or hereafter becomes generally available to the public other than as a result of
a disclosure by you or your representatives or (ii) was available to you on a
nonconfidential basis prior to its disclosure to you by the Company or its
representatives or becomes available to you on a nonconfidential basis, in each
case from a source other than the Company or its representatives, which source
was not itself bound by a confidentiality agreement with the Company or its
representatives and had not received such information, directly or indirectly,
from a Person so bound.

                9.      The Company does not make any representation or warranty
as to the accuracy or completeness of the Information provided to you. Neither
the Company nor any of its representatives shall have any liability resulting
from the use of the Information by you or any of your representatives.

   4

March 9, 2001
Page 4

                10.     Upon our request at any time, you will promptly
redeliver to us all copies of documents containing Information and will promptly
destroy all memoranda, notes and other writings prepared by you or by any Person
referred to in paragraph 2 based on such Information.

                11.     You shall cause each of your Affiliates to comply with
the terms of paragraphs 2, 3, 4, 5, 6, 7, 8 and 10 (construing such paragraphs
for such purposes to refer also to such Affiliates in each instance where there
is a reference to you).

                12.     You acknowledge that irreparable damage would occur to
the Company in the event any of the provisions of this agreement were not
performed in accordance with their specific terms or were otherwise breached.
Accordingly, the Company shall be entitled to an injunction or injunctions to
prevent breaches of the provisions of this agreement and to enforce specifically
the terms and provisions hereof in any court of competent jurisdiction in the
United States of America or any state thereof, in addition to any other remedy
to which the Company may be entitled at law or in equity.

                13.     If any term or provision of this agreement or any
application hereof shall be invalid or unenforceable, the remainder of this
agreement and any other application of such term or provision shall not be
affected thereby.

                14.     This agreement may be executed in any number of
counterparts, each of which when so executed and delivered shall be an original,
but such counterparts shall constitute one and the same instrument.

                15.     This agreement contains the entire understanding of the
parties hereto with respect to the matters covered hereby and may be amended
only by an agreement in writing executed by the Company and you.

                16.     This agreement shall be binding upon, inure to the
benefit of and be enforceable by our respective successors and assigns.

                17.     This agreement shall be governed by and construed in
accordance with the internal laws (as opposed to conflict of law provisions) of
the State of New York.

                                     ******

   5

March 9, 2001
Page 5

                If the foregoing correctly sets forth our agreement as to the
matters set forth herein, please confirm our agreement by executing and
returning a copy of this agreement to the undersigned.

                                   Very truly yours,

                                   BARRETT RESOURCES CORPORATION

                                   By: GOLDMAN, SACHS & CO., as financial
                                       advisor to Barrett Resources Corporation

                                   By: /s/ Goldman Sachs & Co.
                                       -----------------------------------------

                                       Name:
                                       Title:

The foregoing terms are agreed to:

         /s/ Keith Bailey
- ------------------------------------

By: Keith Bailey
   ---------------------------------
    Name:
    Title: Chmn.Pres.CEO

   1
                                                              Exhibit (d) (3)

                            NONDISCLOSURE AGREEMENT

     THE WILLIAMS COMPANIES, INC., a Delaware corporation ("Williams") and
BARRETT RESOURCES CORPORATION, a Delaware corporation ("Recipient"), sometimes
referred to herein individually as a "Party" and collectively as the "Parties",
in consideration of the mutual covenants of this Agreement, hereby agree as
follows:

1.   Recipient has requested information regarding Williams for the purpose of
     evaluating a possible business combination regarding Williams and Recipient
     ("Transaction"). Williams may consider such information proprietary under
     this Agreement either because it has developed the Information internally,
     or because it has received the Information subject to a continuing
     obligation to maintain the confidentiality of the Information, or because
     of other reasons.

2.   The term "Information" as used in this Agreement shall mean information
     regarding Williams or any of its subsidiaries or their respective assets or
     businesses which is furnished to Recipient by Williams or its
     representatives. Williams shall have the right to determine, in its sole
     judgment, what information it shall provide to Recipient.

3.   With respect to Information disclosed under this Agreement, Recipient
     shall:

     a.   Hold the Information in confidence, exercising a degree of care not
          less than the care used by Recipient to protect its own proprietary or
          confidential information that it does not wish to disclose.

     b.   Restrict disclosure of the Information solely to those directors,
          officers, employees, and/or agents/consultants with a need to know for
          the purpose of evaluating the Transaction and not disclose it to any
          other person.

     c.   Advise those persons to whom the Information was disclosed of their
          obligations with respect to the Information. Recipient shall be
          responsible for any breach of this Agreement by its representatives.

     d.   Use the Information only in connection with continuing discussions by
          the Parties concerning the Transaction, except as may otherwise be
          agreed to by Williams in writing.

4.   The Information shall be deemed the property of Williams and, upon request,
     Recipient shall return all Information received in tangible form to
     Williams, without retaining any copy or duplicate thereof, and shall
     destroy any and all written, printed or other material or information
     derived from the Information and provide Williams written certification of
     such document destruction. If Recipient loses or makes an unauthorized
     disclosure of Williams' Information, it shall notify Williams immediately
     and use reasonable efforts to retrieve the lost or wrongfully disclosed
     Information.

5.   Recipient shall have no obligation to preserve the proprietary nature of
     any Information which:

                                                                               1
   2
     a.   was previously known to Recipient free of any obligation to keep it
          confidential;

     b.   is or becomes publicly available by other than unauthorized
          disclosure;

     c.   is received from a third party whose disclosure, to the best of
          Recipient's knowledge, does not violate any confidentiality
          obligation; or

     d.   is disclosed pursuant to the requirement or request of a governmental
          agency or court of competent jurisdiction to the extent such
          disclosure is required by a valid law, regulation or court order, and
          sufficient notice is given by Recipient to Williams of any such
          requirement or request in order to permit Williams to seek an
          appropriate protective order or exemption from such requirement or
          request.

6.   With respect to any information, including but not limited to Information,
     which Williams discloses to Recipient for the purpose of evaluating the
     Transaction, it is understood and agreed that Williams does not make any
     representations or warranties as to the accuracy, completeness or fitness
     for a particular purpose thereof. It is further understood and agreed that
     neither Williams nor its representatives shall have any liability or
     responsibility to Recipient or to any other person or entity resulting from
     the use of any information so furnished or otherwise provided. Neither this
     Agreement, nor the transfer of Information hereunder, shall be construed as
     granting either expressly, by implication, estoppel, or otherwise, any
     license or right to any information or data now or hereafter owned or
     controlled by Williams to Recipient and all such Information shall remain
     the property of Williams.

7.   Neither this Agreement, nor the disclosure of Information under this
     Agreement, nor the ongoing discussions and correspondence between the
     Parties, shall constitute or imply a commitment or binding obligation
     between the Parties or their respective affiliated companies regarding the
     Transaction. If, in the future, the Parties elect to enter into a binding
     commitment regarding the Transaction, such commitment shall be explicitly
     stated in a separate written agreement executed by both Parties, and the
     Parties hereby affirm that they do not intend their discussions,
     correspondence, and other activities to be construed as forming a contract
     regarding the Transaction or any other transaction between them without
     execution of such separate written agreement.

8.   Recipient acknowledges that it is aware (and that prior to the disclosure
     of any Information to any person pursuant to Paragraph 3b such person will
     be advised) that the United States securities laws prohibit any person who
     has material non-public information about a company from purchasing or
     selling securities of such company or from communicating such information
     to any other person under circumstances in which it is reasonably
     foreseeable that such person is likely to purchase or sell such securities.

9.   This Agreement shall benefit and be binding upon the Parties hereto and
     their respective successors and assigns.

10.  This Agreement shall be governed by and construed in accordance with the
     laws of the State of Oklahoma without regard to choice of law principles.

11.  This Agreement shall become effective as of the date set forth below
     ("Effective Date"). The

                                                                               2

   3
     obligations of the Parties under this Agreement shall survive and continue
     beyond the Effective Date for a period of three (3) years.

12.  Recipient acknowledges that in the event of an unauthorized disclosure, the
     damages incurred by Williams may be difficult if not impossible to
     ascertain, and that Williams may seek injunctive relief as well as monetary
     damages against Recipient for breach of this Agreement.

13.  This Agreement constitutes the entire understanding between the Parties
     with respect to the Information provided hereunder. No amendment or
     modification of this Agreement shall be valid or binding on the Parties
     unless made in writing and executed on behalf of each Party by its duly
     authorized representative.

Each Party represents that it has caused this Agreement to be executed on its
behalf as of the date written below by a representative empowered to bind that
Party with respect to the undertakings and obligations contained herein.

Executed and effective this 6th day of May, 2001

THE WILLIAMS COMPANIES, INC.               BARRETT RESOURCES CORPORATION

By:    /s/ MARK D. WILSON                  By:     /s/ EUGENE A. LANG
      ---------------------------                -------------------------------

Name:  Mark D. Wilson                      Name:  Eugene A. Lang
      ---------------------------                -------------------------------

Title: Vice President-Corporate            Title: Executive Vice President,
       Development                                General Counsel and Secretary
      ---------------------------                -------------------------------

                                                                               3