Exhibit 4.1


                         SEVENTH SUPPLEMENTAL INDENTURE

     THIS  SEVENTH  SUPPLEMENTAL  INDENTURE  dated as of March  12,  2007  (this
"Supplemental  Indenture"),  among Pioneer Natural Resources Company, a Delaware
corporation  (the  "Company"),  Pioneer Natural  Resources USA, Inc., a Delaware
corporation,  for  purposes of agreeing to make certain  guarantees  pursuant to
Section 5 hereof (the "Guarantor"),  The Bank of New York Trust Company, N.A., a
national  banking  association  organized under the laws of the United States of
America, as successor trustee under the Indenture (the "Original Trustee"),  and
Wells Fargo Bank, National  Association,  national banking association organized
under the laws of the United States of America,  as series trustee for the Notes
(the "Series Trustee").  Capitalized terms used herein and not otherwise defined
have the meanings set forth in the Indenture referred to below.

                                    RECITALS

     A. The Company  and The Bank of New York,  a New York  banking  corporation
(the "Prior Trustee"),  entered into that certain Indenture, dated as of January
13, 1998 (the "Indenture"),  pursuant to which the Company may from time to time
issue  its  debentures,   notes,   bonds  or  other  evidences  of  indebtedness
(collectively, the "Debt Securities").

     B. The Company,  the Prior Trustee and the Original  Trustee are parties to
that certain Agreement of Resignation,  Appointment and Acceptance,  dated as of
February 21, 2005, pursuant to which the Prior Trustee resigned as trustee under
the Indenture and the Original Trustee was appointed as successor  trustee under
the Indenture.

     C. Section 9.01 of the Indenture provides that the Company, when authorized
by a resolution  of the Board of Directors of the Company,  and the Trustee may,
without  the  consent  of the  holders  of the  Debt  Securities,  enter  into a
supplemental  indenture to establish the form or terms of Debt Securities of any
series as permitted by Sections 2.01 and 2.03 of the Indenture.

     D. Section 7.08 of the  Indenture  provides  that the Company may appoint a
separate Trustee for any one or more series of Debt Securities.

     E. The Company desires to issue,  and upon certain events specified in this
Supplemental  Indenture,  the  Guarantor  desires  to agree to be  obligated  to
guarantee,  $500,000,000  aggregate  principal  amount of 6.65% Senior Notes due
2017 (the  "Notes") and in connection  therewith,  the Company and the Guarantor
have duly determined to make, execute and deliver this Supplemental Indenture to
set forth the terms and provisions of the Notes as required by the Indenture.

     F. The  Company  desires  to  appoint  the  Series  Trustee to serve as the
Trustee  under the  Indenture  with  respect  to, and only with  respect to, the
Notes.

     G. The Company has  requested  that the  Original  Trustee  enter into this
Supplemental  Indenture in connection with the appointment of the Series Trustee
with all the rights, powers, and duties of the Trustee with respect to, and only
with  respect to, the Notes and for the purpose of  supplementing  and  amending
Section 9.01 of the Indenture to effect such appointment.
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     H. The  Company  has  determined   that  this   Supplemental  Indenture  is
authorized  or  permitted  by Sections  9.01 and 7.08 of the  Indenture  and has
delivered to the Original  Trustee and the Series  Trustee an Opinion of Counsel
to that effect and an Opinion of Counsel and Officers' Certificate to the effect
that all conditions precedent provided for in the Indenture to the execution and
delivery of this Supplemental Indenture have been complied with.

     I. All things  necessary  to make this  Supplemental  Indenture a valid and
legally binding indenture and agreement  according to its terms, and a valid and
legally binding amendment of, and supplement to, the Indenture have been done.

     NOW, THEREFORE, in consideration of the mutual agreements and covenants set
forth  herein,  the parties  hereto agree,  subject to the terms and  conditions
hereinafter  set forth, as follows for the benefit of the Series Trustee and the
Holders of the Notes:

                                    AGREEMENT

     Section 1. Appointment and Acceptance by Series Trustee.

     (a) Pursuant to the Indenture and this Supplemental Indenture,  the Company
hereby  appoints the Series  Trustee as Trustee under the Indenture with respect
to, and only with  respect  to, the Notes.  Pursuant to the  Indenture,  all the
rights,  powers and duties of the Trustee under the Indenture shall be vested in
the Series  Trustee  with respect to the Notes,  and there shall  continue to be
vested in the Original  Trustee all of its rights,  powers and duties as Trustee
under the  Indenture  with  respect to all of the series of Debt  Securities  to
which it has served and continues to serve as Trustee under the Indenture.

     (b) The Series Trustee hereby  represents that it is qualified and eligible
under the  provisions of Section 7.10 of the Indenture and the provisions of the
Trust Indenture Act of 1939 to accept its appointment as Trustee with respect to
the Notes  under the  Indenture  and  hereby  accepts  the  appointment  as such
Trustee.

     (c) Pursuant to the Indenture and this Supplemental Indenture,  the Company
hereby appoints the Series Trustee as "Debt Security Registrar," "authentication
agent" and "paying agent" with respect to the Notes.

     Section 2. Notes. Pursuant to Section 2.03 of the Indenture,  the terms and
provisions of the Notes are as follows:

     (a) The title of the Notes shall be "6.65% Senior Notes due 2017."

     (b) The  Notes  shall  be   initially  limited  to  $500,000,000  aggregate
principal  amount.  The Company  may,  without the consent of the Holders of the
Notes, increase such aggregate principal amount in the future, on the same terms
and conditions  and with the same CUSIP numbers as the Notes.  The Company shall
not issue any such  additional  Notes unless the  additional  Notes are fungible
with the Notes for United States federal income tax purposes.

     (c) The Notes shall not require any principal or premium  payments prior to
maturity on March 15, 2017.
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     (d) The rate at which  the Notes  shall  bear  interest  shall be 6.65% per
annum;  interest on the notes shall  accrue from March 12,  2007,  for the first
interest payment and from the most recent interest payment date thereafter;  the
interest payment dates on which such interest shall be payable shall be March 15
and September  15,  beginning  September 15, 2007;  and the record dates for the
determination of the holders of the Notes to whom such interest is payable shall
be the immediately  preceding March 1 (for March 15 payment dates) and September
1 (for  September  15 payment  dates);  the rate at which the overdue  principal
shall bear interest shall be 1% per annum in excess of the rate stated initially
in this clause;  and the rate at which overdue  installments  of interest  shall
bear  interest  shall be 1% per annum in excess of the rate stated  initially in
this clause to the extent lawful.

     (e) Payments of principal of and interest on the Notes  represented  by one
or more Global Senior Notes  initially  registered in the name of The Depository
Trust Company (the  "Depositary") or its nominee with respect to the Notes shall
be made by the Company through the Trustee in immediately available funds to the
Depositary or its nominee, as the case may be.

     (f) The  Notes  shall be  redeemable  at any  time,  at the  option  of the
Company,  in whole or from time to time in part, at the price,  and otherwise in
accordance  with the  terms  and  provisions,  set  forth in  Section  3 of this
Supplemental Indenture and (to the extent they do not conflict with Section 3 of
this Supplemental  Indenture) the terms and provisions of Sections 3.03 and 3.04
of the Indenture.

     (g) The Notes  shall be  represented  by one or more  Global  Senior  Notes
deposited  with the  Depositary and registered in the name of the nominee of the
Depositary.

     (h) There shall be no mandatory sinking fund for the payments of the Notes.

     (i) As long as the Depositary or its nominee, or a successor  Depositary or
its nominee,  is the registered owner of the Global Senior Notes relating to the
Notes, owners of the beneficial  interests in such Global Senior Notes shall not
be entitled to have the Notes registered in their names and shall not receive or
be entitled to receive physical  delivery of Notes in definitive form except (i)
as provided in Section  2.15(c) of the  Indenture or (ii) if an Event of Default
with respect to the Notes has occurred and is continuing.

     (j) Wells Fargo Bank, National  Association shall be the series trustee for
the Notes under the Indenture.

     (k) Article X of the Indenture shall apply to the Notes.

     (l) The Notes  shall not be  subordinated  pursuant  to the  provisions  of
Article XII of the Indenture. The Notes shall be senior unsecured obligations of
the Company  ranking pari passu with other existing and future senior  unsecured
indebtedness of the Company.

     (m) The Company  shall be subject to all the covenants set forth in Article
IV of the Indenture with respect to the Notes.

     (n) To the extent not set forth herein,  the  provisions of Section 2.03 of
the Indenture are not applicable.
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     Section 3. Optional  Redemption  of Notes.  The Notes will be redeemable at
any time,  at the option of the Company,  in whole or from time to time in part,
upon not less  than 30 and not more  than 60 days'  notice  as  provided  in the
Indenture,  on any date prior to  maturity  (the  "Redemption  Date") at a price
equal to 100% of the principal  amount thereof plus accrued and unpaid interest,
if any, to the Redemption Date (subject to the right of Holders of record on the
relevant record date to receive  interest due on any interest  payment date that
is on or prior to the Redemption  Date) plus a Make-Whole  Premium,  if any (the
"Redemption  Price"). In no event will a Redemption Price ever be less than 100%
of the principal amount of the Notes plus accrued and unpaid  interest,  if any,
to the Redemption Date.

     The amount of the  Make-Whole  Premium with respect to any of the Notes (or
portion thereof) to be redeemed will be equal to the excess, if any, of:

     (a) the sum of the present  values,  calculated as of the Redemption  Date,
of:

        (i) each interest payment that, but for such redemption, would have been
payable  on such Note (or  portion  thereof)  being  redeemed  on each  interest
payment date occurring after the Redemption Date (excluding any accrued interest
for the period prior to the Redemption Date); and

        (ii) the principal amount that, but for such redemption, would have been
payable at the final maturity of such Note (or portion  thereof) being redeemed;
over

     (b) the principal amount of such Note (or portion thereof) being redeemed.

     The present values of interest and principal payments referred to in clause
(a) above will be determined in accordance with generally accepted principles of
financial  analysis.  Such present values will be calculated by discounting  the
amount of each  payment of  interest or  principal  from the date that each such
payment would have been payable, but for the redemption,  to the Redemption Date
at a discount rate equal to the Treasury  Yield (as defined below) plus 50 basis
points.

     The  Make-Whole  Premium will be  calculated by an  independent  investment
banking institution of national standing appointed by the Company; provided that
if the Company fails to make such appointment at least 30 business days prior to
the Redemption  Date, or if the  institution so appointed is unwilling or unable
to make  such  calculation,  such  calculation  will  be made by an  independent
investment banking institution of national standing appointed by the Trustee (in
any such case, an "Independent Investment Banker").

     For purposes of determining the Make-Whole Premium,  "Treasury Yield" means
a rate of interest  per annum equal to the weekly  average  yield to maturity of
United States Treasury Notes that have a constant  maturity that  corresponds to
the  remaining  term to  maturity of the  applicable  Notes,  calculated  to the
nearest  1/12th of a year (the  "Remaining  Term").  The Treasury  Yield will be
determined as of the third  business day  immediately  preceding the  applicable
Redemption Date.

     The  weekly  average  yields  of  United  States  Treasury  Notes  will  be
determined by reference to the most recent statistical  release published by the
Federal Reserve Bank of New
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York and  designated  "H.15  (519)  Selected  Interest  Rates" or any  successor
release (the "H.15 Statistical  Release").  If the H.15 Statistical Release sets
forth a weekly average yield for United States  Treasury Notes having a constant
maturity that is the same as the Remaining Term, then the Treasury Yield will be
equal to such weekly average yield. In all other cases,  the Treasury Yield will
be calculated by  interpolation,  on a straight-line  basis,  between the weekly
average yields on the United States Treasury Notes that have a constant maturity
closest to and greater than the Remaining  Term and the United  States  Treasury
Notes that have a constant  maturity closest to and less than the Remaining Term
(in each case as set forth in the H.15 Statistical Release).  Any weekly average
yields so calculated by interpolation  will be rounded to the nearest 1/100th of
1%, with any figure of 1/200th of 1% or above being  rounded  upward.  If weekly
average  yields for United States  Treasury  Notes are not available in the H.15
Statistical Release or otherwise,  then the Treasury Yield will be calculated by
interpolation of comparable rates selected by the Independent Investment Banker.

     In  the  case  of any  partial  redemption,  selection  of  the  Notes  for
redemption  will be made by the Trustee on a pro rata  basis,  by lot or by such
other  method as the  Trustee in its sole  discretion  shall deem to be fair and
appropriate,  although  no such Note of $1,000 in original  principal  amount or
less shall be redeemed in part. If any Note is to be redeemed in part only,  the
notice of  redemption  relating  to such Note  shall  state the  portion  of the
principal amount thereof to be redeemed. A new Note in principal amount equal to
the unredeemed  portion thereof will be issued in the name of the Holder thereof
upon cancellation of the original Note.

     Section 4. Offer to Repurchase Upon a Change of Control Repurchase Event.

     (a) If a Change of Control Repurchase Event occurs,  unless the Company has
otherwise  exercised  its right to redeem the Notes,  the  Company  will make an
offer to each Holder of Notes to repurchase  all or any portion (equal to $1,000
or an  integral  multiple of $1,000) of such  Holder's  Notes at a price in cash
equal  to 101% of the  aggregate  principal  amount  of Notes  repurchased  plus
accrued and unpaid  interest,  if any, on the Notes  repurchased  to the date of
repurchase (the "Change of Control  Repurchase Event  Payment").  Within 30 days
following any Change of Control Repurchase Event, the Company will mail a notice
(the "Change of Control  Repurchase Event Offer") to each holder  describing the
transaction or  transactions  that  constitute the Change of Control  Repurchase
Event and stating:

        (i)   that the Change  of Control  Repurchase  Event Offer is being made
pursuant to the Change of Control  Repurchase  Event provisions of the Notes and
that all Notes tendered will be accepted for payment;

        (ii)  the  purchase  price  and  the  purchase  date, which  shall be no
earlier  than 30 days and no later  than 60 days  from the date  such  notice is
mailed (the "Change of Control Repurchase Event Payment Date");

        (iii) that any Note not tendered will continue to accrue interest;

        (iv)  that, unless the Company defaults  in the payment of the Change of
Control Repurchase Event Payment, all Notes accepted for payment pursuant to the
Change of Control Repurchase Event Offer will cease to accrue interest after the
Change of Control Repurchase Event Payment Date;
                                       5


        (v)   that Holders electing to have  any Notes  purchased pursuant  to a
Change of Control Repurchase Event Offer will be required to surrender the Notes
to the paying agent at the address specified in the notice prior to the close of
business on the third  business day preceding  the Change of Control  Repurchase
Event Payment Date;

        (vi)  that Holders  will be entitled to withdraw  their election  if the
paying  agent  receives,  not later  than the close of  business  on the  second
business day  preceding the Change of Control  Repurchase  Event Payment Date, a
telegram,  telex, facsimile transmission or letter setting forth the name of the
Holder,  the principal  amount of Notes delivered for purchase,  and a statement
that such Holder is withdrawing his election to have the Notes purchased; and

        (vii) that Holders whose Notes  are being purchased only in part will be
issued new Notes equal in  principal  amount to the  unpurchased  portion of the
Notes  surrendered,  which  unpurchased  portion  must be  equal  to  $1,000  in
principal amount or an integral multiple thereof.

     The  Company  will  comply  with the  requirements  of Rule 14e-1 under the
Exchange Act, and any other  securities laws and  regulations  thereunder to the
extent  those  laws  and  regulations  are  applicable  in  connection  with the
repurchase of the Notes as a result of a Change of Control  Repurchase Event. To
the extent that the  provisions of any securities  laws or regulations  conflict
with the Change of Control Repurchase Event provisions of the Notes, the Company
will comply with the applicable  securities laws and regulations and will not be
deemed to have breached its obligations  under the Change of Control  Repurchase
Event provisions of the Notes by virtue of such conflict.

     (b) On the Change of Control  Repurchase  Event Payment  Date,  the Company
will, to the extent lawful:

        (i)   accept  for  payment  all  Notes  or  portions  of  Notes properly
tendered pursuant to the Company's offer;

        (ii)  deposit  with the paying agent  an amount equal  to the  aggregate
purchase price in respect of all Notes or portions of Notes  properly  tendered;
and

        (iii) deliver or cause to be delivered to the Trustee the Notes properly
accepted, together with an Officers' Certificate stating the aggregate principal
amount of Notes or portions of Notes being purchased by the Company.

     The  paying  agent  will  promptly  mail to each  holder of Notes  properly
tendered  the  purchase  price for such  Notes,  and the Trustee  will  promptly
authenticate  and mail (or cause to be transferred by book entry) to each holder
a new Note equal to the principal amount of any unpurchased portion of the Notes
surrendered,   if  any;  provided,   that  each  new  Note  will  be  issued  in
denominations of $1,000 or integral multiples of $1,000.

     (c)  Except  as  described  above  with  respect  to a  Change  of  Control
Repurchase  Event,  the  Indenture  does not contain any other  provisions  that
permit the holders of the Notes to
                                       6


require  the  Company  to  repurchase  or  redeem  the  Notes in the  event of a
takeover, recapitalization or similar transaction.

     (d) The Company will not be required to make a Change of Control Repurchase
Event Offer if a third party makes an offer in the manner applicable to an offer
made  by the  Company,  at the  times  and  otherwise  in  compliance  with  the
requirements  set forth in the  Indenture,  and such third party  purchases  all
Notes properly tendered and not withdrawn under its offer.

     Section 5.  Obligation to Guarantee.  If at any time any of the Company's 8
1/4% Senior Notes due 2007, 6.50% Senior Notes due 2008, 5.875% Senior Notes due
2012, 5.875% Senior Notes due 2016, 6.875% Senior Notes due 2018 or 7.20% Senior
Notes due 2028 (the "7.20% Notes," and collectively with all other senior notes,
the "Existing  Senior  Notes") are  guaranteed by the Guarantor  pursuant to the
terms of the Indenture or any applicable  supplemental indenture related to such
senior notes,  then the Company,  the Guarantor and the Trustee shall as soon as
reasonably  practicable  thereafter execute and deliver a supplemental indenture
to the Indenture pursuant to which the Guarantor shall unconditionally guarantee
the Notes on substantially the same terms as the Guarantor shall have guaranteed
the 7.20% Notes;  provided,  however,  that if the  Guarantor is not required to
guarantee the 7.20% Notes or if the 7.20% Notes are no longer outstanding,  then
the Guarantor shall guarantee the Notes on  substantially  the same terms as the
most recently issued series of Existing  Senior Notes that are  guaranteed.  The
Company,  the Guarantor and the Trustee,  as applicable,  also shall execute and
deliver such other  documents,  instruments  or  certificates  as are reasonably
necessary or appropriate to effect the required guarantee of the Notes.

     Section 6. Amendments to Sections 1.01, 2.02, 2.07, 2.15 and 13.03.

     (a) Section 1.01.  Section 1.01 is hereby  amended,  solely with respect to
the Notes, by:

        (i)   deleting  clause   (a)(iv)(A)  of   the  definition  of  "Adjusted
Consolidated  Net  Tangible  Assets" and  substituting  therefor  the  following
language  "the net book value of other  tangible  assets of the  Company and its
Subsidiaries,  as of a date no  earlier  than the date of the  Company's  latest
annual or quarterly financial  statement,  and"; deleting the following language
"Issue Date (including, without limitation, under the Credit Agreements)" at the
end of clause  (e) of the  definition  of  "Permitted  Liens"  and  substituting
therefor the following  language  "date on which the 6.65% Senior Notes due 2017
of the Company were originally issued"; adding the following language "and Liens
securing Non-Recourse Indebtedness; provided, however, that the related purchase
money Indebtedness and Non-Recourse  Indebtedness,  as applicable,  shall not be
secured by any  Property or assets of the company or any  Restricted  Subsidiary
other than the  Property  acquired  by the  Company  with the  proceeds  of such
purchase money Indebtedness or Non-Recourse  Indebtedness,  as applicable" after
"Purchase Money Liens" in clause (i) of the definition of "Permitted Liens";

        (ii)  deleting the  definition  of "Credit Agreements"  and substituting
therefor the definition "Credit Facility" as follows:
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     "Credit  Facility"  means,  with  respect to the  Company,  the credit
     facility  made  available  to the Company  pursuant to the Amended and
     Restated 5-Year  Revolving  Credit Agreement dated as of September 30,
     2005,  among the Company and the lenders named therein,  together with
     any Refinancings  thereof by a lender or a syndicate of lenders. It is
     understood  and agreed  that the Credit  Facility  may be  refinanced,
     refunded,  extended,  renewed or  replaced  (through  one or more such
     refinancings,  refundings, extensions, renewals or replacements), as a
     whole,  or in part,  from time to time  after the  termination  of the
     applicable Credit Facility"; and

        (iii) adding a definition of "Change of Control" as follows:

"Change of Control" means the occurrence of any of the following events:

        (a)   any "person" or "group" (as such terms are used in Sections  13(d)
and  14(d) of the  Exchange  Act or any  successor  provisions  to either of the
foregoing) of persons become the  "beneficial  owners" (as defined in Rule 13d-3
under the Exchange Act, except that a person will be deemed to have  "beneficial
ownership" of all shares that any such person has the right to acquire,  whether
such  right is  exercisable  immediately  or only  after the  passage  of time),
directly or indirectly, of more than 50% of the total voting power of the Voting
Stock of the Company,  whether as a result of the issuance of  securities of the
Company, any merger, consolidation, liquidation or dissolution of the Company or
otherwise; or

        (b)   the   sale,  transfer,  assignment,  lease,  conveyance  or  other
disposition,  directly or indirectly,  of all or substantially all the assets of
the  Company  and  its  subsidiaries,  considered  as  a  whole  (other  than  a
disposition  of such  assets as an  entirety  or  virtually  as an entirety to a
wholly-owned   subsidiary)   shall  have  occurred,   or  the  Company   merges,
consolidates  or  amalgamates  with or into any other person or any other person
merges,  consolidates or amalgamates with or into the Company, in any such event
pursuant to a transaction in which the  outstanding  Voting Stock of the Company
is reclassified into or exchanged for cash, securities or other property,  other
than any such transaction where:

              (i)  the outstanding Voting Stock  of the Company is  reclassified
into or  exchanged  for other Voting Stock of the Company or for Voting Stock of
the surviving corporation, and

              (ii) the holders  of the Voting  Stock of the  Company immediately
prior to such transaction own, directly or indirectly,  not less than a majority
of the Voting  Stock of the  Company or the  surviving  corporation  immediately
after such  transaction and in  substantially  the same proportion as before the
transition; or

        (c)   during any period, individuals who at the beginning of such period
constituted  the  Board of  Directors  (together  with any new  directors  whose
election or  appointment  by such Board or whose  nomination for election by the
stockholders  of the Company was  approved by a vote of not less than a majority
of the directors then still in
                                       8


office  who were  either  directors  at the  beginning  of such  period or whose
election or nomination  for election was  previously so approved)  cease for any
reason to constitute a majority of the Board of Directors then in office; or

        (d)   the stockholders of the Company shall have  approved  any  plan of
liquidation or dissolution of the Company.

        (iv)  adding  a definition  of "Change of Control  Repurchase Event"  as
follows:

"Change of Control  Repurchase  Event" means the  occurrence of both a Change of
Control and a Rating Decline.

        (v)   adding a definition of "Investment Grade" as follows:

"Investment Grade" means BBB- or higher by S&P and Baa3 or higher by Moody's, or
the equivalent of such ratings by S&P or Moody's,  or, if either S&P and Moody's
shall not make a rating on the notes publicly available, another Rating Agency.

        (vi)  adding a definition of "Moody's" as follows:

"Moody's" means Moody's Investors Service, Inc.

        (vii) adding a definition of "Non-Recourse Indebtedness" as follows:

"Non-Recourse  Indebtedness"  means Indebtedness or that portion of Indebtedness
of the Company incurred in connection with the acquisition by the Company of any
Property and as to which:

        (a)   the holders of such  Indebtedness  agree in writing that they will
look solely to the  Property so acquired  and  securing  such  Indebtedness  for
payment on or in respect of such Indebtedness and

        (b)   no default  with respect to  such Indebtedness would permit (after
notice  or  passage  of time or  both),  according  to the  terms  of any  other
Indebtedness of the Company or a Restricted Subsidiary, any holder of such other
Indebtedness  to declare a default  under such other  Indebtedness  or cause the
payment of such other  Indebtedness  to be  accelerated  or payable prior to its
stated maturity.

        (viii)adding a definition of "Rating Agency" as follows:

"Rating  Agency"  means  each of S&P and  Moody's,  or if S&P or Moody's or both
shall not make a rating on the notes publicly available, a nationally recognized
statistical  rating  agency or  agencies,  as the case may be,  selected  by the
Company (as certified by a resolution of the Company's board of directors) which
shall be substituted for S&P or Moody's, or both, as the case may be.
                                       9


        (ix)  adding a definition of "Refinance" as follows:

"Refinance" means, in respect of any Indebtedness,  to refinance, extend, renew,
refund, repay, prepay, redeem, defease or retire, or to issue other Indebtedness
in  exchange  or   replacement   for,  such   indebtedness.   "Refinanced"   and
"Refinancing" shall have correlative meanings.

        (x)   adding a definition of "Rating Decline" as follows:

"Rating Decline" means the rating of the notes shall be decreased by one or more
gradations  (including  gradations  within  categories as well as between rating
categories) by each of the Rating Agencies,  provided, however, if the rating of
the notes by each of the Rating  Agencies  is  Investment  Grade,  then  "Rating
Decline"  will mean the rating of the notes  shall be  decreased  by one or more
gradations  (including  gradations  within  categories as well as between rating
categories) by each Rating Agency so that the rating of the notes by each of the
Rating Agencies falls below  Investment  Grade, on any date from the date of the
public notice of an  arrangement  that could result in a Change of Control until
the end of the 30-day period  following  public notice of the  occurrence of the
Change of Control  (which  30-day period shall be extended so long as the rating
of the notes is under publicly announced consideration for possible downgrade by
either of the Rating Agencies; provided, that the other Rating Agency has either
downgraded,  or  publicly  announced  that it is  considering  downgrading,  the
notes).

        (xi)  adding a definition of "S&P" as follows:

"S&P" means Standard & Poor's Ratings  Services,  a division of The  McGraw-Hill
Companies, Inc.

        (xii) adding a definition of "Voting Stock" as follows:

"Voting  Stock"  of any  person  means all  classes  of  capital  stock or other
interests (including  partnership interests) of such person then outstanding and
normally  entitled (without regard to the occurrence of any contingency) to vote
in the election of directors, managers or trustees thereof.

     (b) Section 2.02.  Section 2.02 is hereby  amended,  solely with respect to
the Notes, by deleting the form of the Trustee's  Certificate of  Authentication
and substituting therefore the following:

                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

     This  is one of the  Debt  Securities  of  the  series  designated  therein
referred to in the within-mentioned Indenture.

                                         Dated:

                                         WELLS FARGO BANK, NATIONAL ASSOCIATION,
                                       10


                                         as Trustee


                                         By:  __________________________________
                                              Authorized Signature

     (c) Section 2.07.  Section 2.07 is hereby  amended,  solely with respect to
the Notes,  by adding  "the  Underwriters,"  before  "the  Company"  in the last
sentence of Section 2.07.

     (d) Section 2.15.  Section 2.15 is hereby  amended,  solely with respect to
the Notes,  by adding  "the  Underwriters,"  before  "the  Company" in the third
sentence of subclause (v) of Section 2.15(c).

     (e) Section 13.03. Section 13.03 is hereby amended,  solely with respect to
the Notes, by deleting the second sentence  thereof and  substituting  therefore
the following:

     Except as otherwise expressly provided in this Indenture,  any notice,
     direction,  request  or demand by the  Company  or by any Holder to or
     upon the  Trustee  may be given or made,  for all  purposes,  by being
     deposited  postage  prepaid in a post office  letter box in the United
     States  addressed to the corporate  trust office of the Trustee at 201
     Main Street, Suite 301, Fort Worth, Texas 76102; Attention:  Corporate
     Trust Trustee Administration.

     Section 7. Ratification.  This Supplemental Indenture is executed and shall
be construed as an indenture  supplemental  to the Indenture and, as provided in
the Indenture, this Supplemental Indenture forms a part of the Indenture. Except
to the extent amended by or supplemented  by this  Supplemental  Indenture,  the
Company,  the Guarantor and the Trustee hereby ratify,  confirm and reaffirm the
Indenture in all respects.

     Section 8. Counterparts. This Supplemental Indenture may be executed in any
number of counterparts,  each of which so executed shall be an original, but all
such counterparts shall together constitute but one and the same instrument.

     Section 9.  Governing  Law.  The laws of the State of New York shall govern
the construction and  interpretation  of this  Supplemental  Indenture,  without
regard to principles of conflicts of laws.

     Section 10. Trustee Not Responsible for Recitals or Issuance of Notes.  The
recitals  contained  herein  and in  the  Notes,  except  the  Series  Trustee's
certificates of authentication, shall be taken as the statements of the Company,
and the Series  Trustee and the Original  Trustee assume no  responsibility  for
their  correctness.  The  Series  Trustee  and  the  Original  Trustee  make  no
representations as to the validity or sufficiency of this Supplemental Indenture
or of the Notes.  The  Series  Trustee  and the  Original  Trustee  shall not be
accountable  for the use or  application by the Company of Notes or the proceeds
thereof.

                            [Signature Page Follows]
                                       11


     IN WITNESS  WHEREOF,  the parties  hereto  have  caused  this  Supplemental
Indenture to be signed on their behalf by their duly authorized  representatives
as of the date first above written:



                                 Pioneer Natural Resources Company



                                 By:    /s/ Mark H. Kleinman
                                        ----------------------------------------
                                 Name:  Mark H. Kleinman
                                 Title: Vice President, Corporate Secretary and
                                        Chief Compliance Officer


                                 Pioneer Natural Resources USA, Inc.



                                 By:    /s/ Mark H. Kleinman
                                        ----------------------------------------
                                 Name:  Mark H. Kleinman
                                 Title: Vice President, Corporate Secretary and
                                        Chief Compliance Officer


                                 Wells Fargo Bank, National Association,
                                 as Series Trustee



                                 By:    /s/ Patrick T. Giordano
                                        ----------------------------------------
                                 Name:  Patrick T. Giordano
                                 Title: Vice President


                                 The Bank of New York Trust Company, N.A.,
                                 as Original Trustee



                                 By:    /s/ Mauri J. Cowen
                                        ----------------------------------------
                                 Name:  Mauri J. Cowen
                                 Title: Vice President


                                 SIGNATURE PAGE
                         SEVENTH SUPPLEMENTAL INDENTURE