EXHIBIT 10.10

                                 AMENDMENT NO. 1
                                     TO THE
                       PIONEER NATURAL RESOURCES USA, INC.
                            401(k) AND MATCHING PLAN
             (Amended and Restated Effective as of January 1, 2002)
             ------------------------------------------------------

     Pursuant to the  provisions  of Section 8.1  thereof,  the Pioneer  Natural

Resources USA, Inc. 401(k) and Matching Plan (Amended and Restated  Effective as

of January 1, 2002) (the  "Plan") is hereby  amended in the  following  respects

only:

     FIRST: Effective January 1, 2002, the first two sentences of Section 4.2 of

the Plan are hereby amended by restatement as three  sentences  which shall read

as follows:

             For investment purposes the Trust shall be divided into the Pioneer
         Stock Investment Fund, which shall be a common fund invested in Pioneer
         Stock,  and such  number  and  kind  of  other  separate  and  distinct
         Investment  Funds  as the  Committee shall  determine  in its  absolute
         discretion.  The Trust assets allocated to a particular Investment Fund
         other  than the Pioneer  Stock Investment Fund shall be invested by the
         Trustee  and/or one  or more  investment  managers  duly  appointed  in
         accordance  with the  provisions  of the  Trust, as the case may be, in
         such type of property, whether real, personal or mixed,  as the Trustee
         is directed to acquire and hold for such Investment Fund. Dividends and
         other  amounts  received  with  respect to  Pioneer  Stock held  in the
         Pioneer Stock Investment Fund shall be invested in Pioneer Stock.

     SECOND: Effective January 1, 2002, the third sentence of Section 4.3 of the

Plan is hereby deleted in its entirety.

     THIRD:  Effective  January  1, 2002,  Section  6.1(c) of the Plan is hereby

amended by restatement in its entirety to read as follows:

             (c) Subject  to  the  provisions  of  this  Article  requiring that
         distributions  and  withdrawals  be  made  in the  form  of an  annuity
         contract,  distributions and withdrawals shall be made in cash,  except
         that amounts  credited to an  Account  that are invested in the Pioneer
         Stock  Investment  Fund may,  at the  election  of the  Participant, be
         distributed  in  the  form  of  Pioneer  Stock  with  cash  in  lieu of
         fractional shares.

     FOURTH:  Effective  October 1, 2002,  Section  6.6(a) of the Plan is hereby

amended by restatement in its entirety to read as follows:






             (a) A Participant in the employ of an Employer may make --

                    (i)      a withdrawal  of all or a portion  (in multiples of
                             10% or in whole dollar amounts) of the total amount
                             credited  to his  or her  After-Tax  Account,  Mesa
                             After-Tax Account or Rollover Account;

                     (ii)    if the Participant  has attained the age of 59 1/2,
                             a withdrawal  of all or a portion  (in multiples of
                             10% or in whole dollar amounts) of the total vested
                             amount credited to his or her Accounts  (other than
                             his or her Matching Plan Account  and Mesa  Premium
                             Account); or

                    (iii)    a  hardship  withdrawal  of  such  amount   as  the
                             Committee  shall   determine  to  be  necessary  to
                             satisfy an  immediate and  heavy financial  need of
                             such Participant  from his or her  Pre-Tax  Account
                             and Prior Plan Pre-Tax Account, other than earnings
                             credited to either  such Account for  any period of
                             time  after  December  31,   1988,  and   qualified
                             nonelective contributions allocated  to either such
                             Account;

             provided, however, that (i) no withdrawal may be made unless notice
             of such withdrawal is  delivered to or  in the manner prescribed by
             the Committee by the withdrawing  Participant within such period of
             time prior  to the  effective  date  thereof  as the  Committee may
             prescribe in  its discretion,  (ii) no withdrawal  may be made by a
             Participant  to whom  a loan  from the  Trust  is then  outstanding
             unless  the  Committee is  satisfied  that  such  loan will  remain
             nontaxable  and  fully  secured  by the  withdrawing  Participant's
             Vested Interest  following such  withdrawal,  and (iii) withdrawals
             from the Prior Plan Pre-Tax Account and Prior Plan Employer Account
             may be made only pursuant to the notice and consent requirements of
             Section  6.2(b).   The  Committee  shall   direct  the  Trustee  to
             distribute  any withdrawn  amount to such  Participant  as  soon as
             practicable  following the  effective date of the  withdrawal.  Any
             withdrawal from an  Account pursuant to this Section shall be taken
             proportionally from each  Investment Fund in  which such Account is
             invested;  provided,  however,  that a Participant may elect in the
             manner prescribed  by the  Committee to have  his or her withdrawal
             taken from the portion of such  Account that is  invested in one or
             more Investment Fund(s).  The Committee may  prescribe uniform  and
             nondiscriminatory rules and procedures limiting the number of times
             that a Participant  may make withdrawals during a Plan Year and the
             minimum  amount  that a  Participant  may  withdraw  on  any single
             occasion.


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     IN WITNESS WHEREOF, this Amendment has been executed as of this 10th day of
January, 2003.

                                         PIONEER NATURAL RESOURCES USA INC.




                                         By   /s/ Larry Paulsen
                                            ---------------------------------
                                              Larry Paulsen, Vice President




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