EXHIBIT 99.6




                                                               December 11, 2001

                            EXCHANGE AGENT AGREEMENT

Citibank, N.A.
111 Wall Street,  14th Floor
New York, New York 10043
Attention: Agency & Trust Services

Ladies and Gentlemen:

               Transcontinental Gas Pipe Line Corporation, a Delaware
corporation (the "Company") proposes to make an offer (the "Exchange Offer") to
exchange all of its outstanding 7% Series A Notes due August 15, 2011 (the "Old
Notes") for its 7% Series B Notes due August 15, 2011 (the "New Notes"). The
terms and conditions of the Exchange Offer as currently contemplated are set
forth in a prospectus, dated December 11, 2001 (the "Prospectus"), proposed to
be distributed to all record holders of the Old Notes. The Old Notes and the New
Notes are collectively referred to herein as the "Notes".

               The Company hereby appoints Citibank, N.A. to act as exchange
agent (the "Exchange Agent") in connection with the Exchange Offer. References
hereinafter to "you" shall refer to Citibank, N.A..

               The Exchange Offer is expected to be commenced by the Company on
or about December 11, 2001. The Letter of Transmittal accompanying the
Prospectus (or in the case of book-entry securities, the Automated Tender Offer
Program ("ATOP") of the Book-Entry Transfer Facility (as defined below)) is to
be used by the holders of the Old Notes to accept the Exchange Offer and
contains instructions with respect to the delivery of certificates for Old Notes
tendered in connection therewith.

               The Exchange Offer shall expire at 5:00 p.m., New York City time,
on January 10, 2002 or on such subsequent date or time to which the Company may
extend the Exchange Offer (the "Expiration Date"). Subject to the terms and
conditions set forth in the Prospectus, the Company expressly reserves the right
to extend the Exchange Offer from time to time and may extend the Exchange Offer
by giving oral (promptly confirmed in writing) or written notice to you before
9:00 a.m., New York City time, on the business day following the previously
scheduled Expiration Date.

               The Company expressly reserves the right to amend or terminate
the Exchange Offer, and not to accept for exchange any Old Notes not theretofore
accepted for exchange, upon the occurrence of any of the conditions of the
Exchange Offer specified in the Prospectus under the caption "The Exchange Offer
- -- Conditions to the Exchange Offer." The Company will give oral (promptly
confirmed in writing) or






written notice of any amendment, termination or nonacceptance to you as promptly
as practicable.

               In carrying out your duties as Exchange Agent, you are to act in
accordance with the following instructions:

               1. You will perform such duties and only such duties as are
specifically set forth in the section of the Prospectus captioned "The Exchange
Offer" or as specifically set forth herein; provided, however, that in no way
will your general duty to act in good faith be discharged by the foregoing.

               2. You will establish a book-entry account with respect to the
Old Notes at The Depository Trust Company (the "Book-Entry Transfer Facility")
for purposes of the Exchange Offer within two business days after the date of
the Prospectus, and any financial institution that is a participant in the
Book-Entry Transfer Facility's systems may make book-entry delivery of the Old
Notes by causing the Book-Entry Transfer Facility to transfer such Old Notes
into your account in accordance with the Book-Entry Transfer Facility's
procedure for such transfer.

               3. You are to examine each of the Letters of Transmittal and
certificates for Old Notes (or confirmation of book-entry transfer into your
account at the Book-Entry Transfer Facility) and any other documents delivered
or mailed to you by or for holders of the Old Notes to ascertain whether: (i)
the Letters of Transmittal and any such other documents are duly executed and
properly completed in accordance with instructions set forth therein; and (ii)
the Old Notes have otherwise been properly tendered. In each case where the
Letter of Transmittal or any other document has been improperly completed or
executed or any of the certificates for Old Notes are not in proper form for
transfer or some other irregularity in connection with the acceptance of the
Exchange Offer exists, you will endeavor to inform the presenters of the need
for fulfillment of all requirements and to take any other action as may be
reasonably necessary or advisable to cause such irregularity to be corrected.

               4. With the approval of the Chairman of the Board of Directors,
President, Senior Vice President, Controller, or any Vice President of the
Company (such approval, if given orally, to be promptly confirmed in writing) or
any other party designated in writing, by such an officer, you are authorized to
waive any irregularities in connection with any tender of Old Notes pursuant to
the Exchange Offer.

               5. Tenders of Old Notes may be made only as set forth in the
Letter of Transmittal and in the section of the Prospectus captioned "The
Exchange Offer -- Procedures for Tendering Old Notes", and Old Notes shall be
considered properly tendered to you only when tendered in accordance with the
procedures set forth therein.

               Notwithstanding the provisions of this Section 5, Old Notes which
the Chairman of the Board, President, Senior Vice President, Controller, or any
Vice





President of the Company shall approve as having been properly tendered shall be
considered to be properly tendered (such approval, if given orally, shall be
promptly confirmed in writing).

               6. You shall advise the Company with respect to any Old Notes
received subsequent to the Expiration Date and accept its instructions with
respect to disposition of such Old Notes.

               7. You shall accept tenders:

                  (a) in cases where the Old Notes are registered in two or more
names only if signed by all named holders;

                  (b) in cases where the signing person (as indicated on the
Letter of Transmittal) is acting in a fiduciary or a representative capacity
only when proper evidence of his or her authority so to act is submitted; and

                  (c) from persons other than the registered holder of Old
Notes, provided that customary transfer requirements, including payment of any
applicable transfer taxes, are fulfilled.

               You shall accept partial tenders of Old Notes where so indicated
and as permitted in the Letter of Transmittal and deliver certificates for Old
Notes to the registrar for split-up and return any untendered Old Notes to the
holder (or such other person as may be designated in the Letter of Transmittal)
as promptly as practicable after expiration or termination of the Exchange
Offer.

               8. Upon satisfaction or waiver of all of the conditions to the
Exchange Offer, the Company will notify you (such notice, if given orally, to be
promptly confirmed in writing) of its acceptance, promptly after the Expiration
Date, of all Old Notes properly tendered and you, on behalf of the Company, will
exchange such Old Notes for New Notes and cause such Old Notes to be cancelled.
Delivery of New Notes will be made on behalf of the Company by you at the rate
of $1,000 principal amount of New Notes for each $1,000 principal amount of the
corresponding series of Old Notes tendered promptly after notice (such notice if
given orally, to be promptly confirmed in writing) of acceptance of said Old
Notes by the Company; provided, however, that in all cases, Old Notes tendered
pursuant to the Exchange Offer will be exchanged only after timely receipt by
you of certificates for such Old Notes (or confirmation of book-entry transfer
into your account at the Book-Entry Transfer Facility), a properly completed and
duly executed Letter of Transmittal (or manually signed facsimile thereof) with
any required signature guarantees and any other required documents. You shall
issue New Notes only in denominations of $1,000 or any integral multiple
thereof.




               9. Tenders pursuant to the Exchange Offer are irrevocable, except
that, subject to the terms and upon the conditions set forth in the Prospectus
and the Letter of Transmittal, Old Notes tendered pursuant to the Exchange Offer
may be withdrawn at any time prior to the Expiration Date.

               10. The Company shall not be required to exchange any Old Notes
tendered if any of the conditions set forth in the Exchange Offer are not met.
Notice of any decision by the Company not to exchange any Old Notes tendered
shall be given (if given orally, to be promptly confirmed in writing) by the
Company to you.

               11. If, pursuant to the Exchange Offer, the Company does not
accept for exchange all or part of the Old Notes tendered because of an invalid
tender, the occurrence of certain other events set forth in the Prospectus under
the caption "The Exchange Offer -- Conditions to the Exchange Offer" or
otherwise, you shall as soon as practicable after the expiration or termination
of the Exchange Offer return those certificates for unaccepted Old Notes (or
effect appropriate book-entry transfer), together with any related required
documents and the Letters of Transmittal relating thereto that are in your
possession, to the persons who deposited them.

               12. All certificates for reissued Old Notes, unaccepted Old Notes
or for New Notes shall be forwarded by first-class mail.

               13. You are not authorized to pay or offer to pay any
concessions, commissions or solicitation fees to any broker, dealer, bank or
other persons or to engage or utilize any person to solicit tenders.

               14. As Exchange Agent hereunder you:

                  (a) shall not be liable for any action or omission to act
unless the same constitutes your own gross negligence, willful misconduct or bad
faith, and in no event shall you be liable to a securityholder, the Company or
any third party for special, indirect or consequential damages, or lost profits,
arising in connection with this Agreement.

                  (b) shall have no duties or obligations other than those
specifically set forth herein or as may be subsequently agreed to in writing
between you and the Company;

                  (c) will be regarded as making no representations and having
no responsibilities as to the validity, sufficiency, value or genuineness of any
of the certificates or the Old Notes represented thereby deposited with you
pursuant to the Exchange Offer, and will not be required to and will make no
representation as to the validity, value or genuineness of the Exchange Offer;





                  (d) shall not be obligated to take any legal action hereunder
which might in your judgment involve any expense or liability, unless you shall
have been furnished with indemnity satisfactory to you;

                  (e) may conclusively rely on and shall be protected in acting
in reliance upon any certificate, instrument, opinion, notice, letter, telegram
or other document or security delivered to you and believed by you to be genuine
and to have been signed or presented by the proper person or persons;

                  (f) may act upon any tender, statement, request, document,
agreement, certificate or other instrument whatsoever not only as to its due
execution and validity and effectiveness of its provisions, but also as to the
truth and accuracy of any information contained therein, which you shall in good
faith believe to be genuine or to have been signed or presented by the proper
person or persons;

                  (g) may conclusively rely on and shall be protected in acting
upon written or oral instructions from any authorized officer of the Company;

                  (h) may consult with counsel of your selection with respect to
any questions relating to your duties and responsibilities and the advice or
opinion of such counsel shall be full and complete authorization and protection
in respect of any action taken, suffered or omitted to be taken by you hereunder
in good faith and in accordance with the advice or opinion of such counsel; and

                  (i) shall not advise any person tendering Old Notes pursuant
to the Exchange Offer as to the wisdom of making such tender or as to the market
value or decline or appreciation in market value of any Old Notes.

               15. You shall take such action as may from time to time be
requested by the Company (and such other action as you may deem appropriate) to
furnish copies of the Prospectus, Letter of Transmittal and the Notice of
Guaranteed Delivery (as defined in the Prospectus) or such other forms as may be
approved from time to time by the Company, to all persons requesting such
documents and to accept and comply with telephone requests for information
relating to the Exchange Offer, provided that such information shall relate only
to the procedures for accepting (or withdrawing from) the Exchange Offer. The
Company will furnish you with copies of such documents on your request. All
other requests for information relating to the Exchange Offer shall be directed
to the Company, Attention: Richard Carson.

               16. You shall advise by facsimile transmission Richard Carson, a
Senior Attorney of the Company (at the facsimile number (918) 573-4503), and
such other person or persons as the Company may request, daily (and more
frequently during the week immediately preceding the Expiration Date if
requested) up to and including the Expiration Date, as to the number of Old
Notes which have been tendered pursuant to the Exchange Offer and the items
received by you pursuant to this Agreement, separately





reporting and giving cumulative totals as to items properly received and items
improperly received. In addition, you will also inform, and cooperate in making
available to, the Company or any such other person or persons upon oral request
made from time to time prior to the Expiration Date of such other information as
they may reasonably request. Such cooperation shall include, without limitation,
the granting by you to the Company and such person as the Company may request of
access to those persons on your staff who are responsible for receiving tenders,
in order to ensure that immediately prior to the Expiration Date the Company
shall have received information in sufficient detail to enable it to decide
whether to extend the Exchange Offer. You shall prepare a final list of all
persons whose tenders were accepted, the aggregate principal amount of Old Notes
tendered, the aggregate principal amount of Old Notes accepted and deliver said
list to the Company.

               17. Letters of Transmittal and Notices of Guaranteed Delivery
shall be stamped by you as to the date and, after the expiration of the Exchange
Offer, the time, of receipt thereof and shall be preserved by you for a period
of time at least equal to the period of time you preserve other records
pertaining to the transfer of securities. You shall dispose of unused Letters of
Transmittal and other surplus materials by returning them to the Company.

               18. For services rendered as Exchange Agent hereunder, you shall
be entitled to such compensation as set forth on Schedule I attached hereto. The
provisions of this section shall survive the termination of this Agreement.

               19. You hereby acknowledge receipt of the Prospectus and the
Letter of Transmittal. Any inconsistency between this Agreement, on the one
hand, and the Prospectus and the Letter of Transmittal (as they may be amended
from time to time), on the other hand, shall be resolved in favor of the latter
two documents, except with respect to your duties, liabilities and
indemnification as Exchange Agent.

               20. The Company covenants and agrees to fully indemnify and hold
you harmless against any and all loss, liability, cost or expense, including
attorneys' fees and expenses, incurred without gross negligence or willful
misconduct on your part, arising out of or in connection with any act, omission,
delay or refusal made by you in reliance upon any signature, endorsement,
assignment, certificate, order, request, notice, instruction or other instrument
or document believed by you to be valid, genuine and sufficient and in accepting
any tender or effecting any transfer of Old Notes believed by you in good faith
to be authorized, and in delaying or refusing in good faith to accept any
tenders or effect any transfer of Old Notes. In each case, the Company shall be
notified by you, by letter or facsimile transmission, of the written assertion
of a claim against you or of any other action commenced against you, promptly
after you shall have received any such written assertion or shall have been
served with a summons in connection therewith. The Company shall be entitled to
participate at its own expense in the defense of any such claim or other action
and, if the Company so elects, the Company shall





assume the defense of any suit brought to enforce any such claim. In the event
that the Company shall assume the defense of any such suit, the Company shall
not be liable for the fees and expenses of any additional counsel thereafter
retained by you, so long as the Company shall retain counsel satisfactory to you
to defend such suit, and so long as you have not determined, in your reasonable
judgment, that a conflict of interest exists between you and the Company. The
provisions of this section shall survive the termination of this Agreement.

               21. You shall arrange to comply with all requirements under the
tax laws of the United States, including those relating to missing Tax
Identification Numbers, and shall file any appropriate reports with the Internal
Revenue Service.

               22. You shall deliver or cause to be delivered, in a timely
manner to each governmental authority to which any transfer taxes are payable in
respect of the exchange of Old Notes, the Company's check in the amount of all
transfer taxes so payable; provided, however, that you shall reimburse the
Company for amounts refunded to you in respect of your payment of any such
transfer taxes, at such time as such refund is received by you.

               23. This Agreement and your appointment as Exchange Agent
hereunder shall be construed and enforced in accordance with the laws of the
State of New York applicable to agreements made and to be performed entirely
within such state, and without regard to conflicts of law principles, and shall
inure to the benefit of, and the obligations created hereby shall be binding
upon, the successors and assigns of each of the parties hereto.

               24. This Agreement may be executed in two or more counterparts,
each of which shall be deemed to be an original and all of which together shall
constitute one and the same agreement.

               25. In case any provision of this Agreement shall be invalid,
illegal or unenforceable, the validity, legality and enforceability of the
remaining provisions shall not in any way be affected or impaired thereby.

               26. This Agreement shall not be deemed or construed to be
modified, amended, rescinded, cancelled or waived, in whole or in part, except
by a written instrument signed by a duly authorized representative of the party
to be charged. This Agreement may not be modified orally.

               27. Unless otherwise provided herein, all notices, requests and
other communications to any party hereunder shall be in writing (including
facsimile or similar writing) and shall be given to such party, addressed to it,
at its address or telecopy number set forth below:




                        If to the Company:

                                    Transcontinental Gas Pipe Line Corporation
                                    c/o The Williams Companies, Inc.
                                    One Williams Center
                                    Tulsa, Oklahoma  74172

                                    Facsimile:  918-573-4503
                                    Attention:  Richard Carson

                        If to the Exchange Agent:

                                    Citibank, N.A.
                                    111 Wall Street,  5th Floor
                                    New York, New York  10043

                                    Facsimile:  (212) 657-4024
                                    Attention:  Global Agency & Trust Services

               28. Unless terminated earlier by the parties hereto, this
Agreement shall terminate 90 days following the Expiration Date. Notwithstanding
the foregoing, Sections 18 and 20 shall survive the termination of this
Agreement. Upon any termination of this Agreement, you shall promptly deliver to
the Company any certificates for Notes, funds or property then held by you as
Exchange Agent under this Agreement.

               29. This Agreement shall be binding and effective as of the date
hereof.






               Please acknowledge receipt of this Agreement and confirm the
arrangements herein provided by signing and returning the enclosed copy.

                                          TRANSCONTINENTAL GAS PIPE
                                            LINE CORPORATION


                                          By:
                                             ----------------------------------
                                          Name:
                                          Title:




Accepted as of the date
first above written:

CITIBANK, N.A., as Exchange Agent


By:
   --------------------------------
Name:
Title:







                                   SCHEDULE I
                         COMPENSATION OF EXCHANGE AGENT:



[To Come]