EXHIBIT 10.13

                                 AMENDMENT NO. 4
                                     TO THE
          PIONEER NATURAL RESOURCES USA, INC. 401(k) AND MATCHING PLAN
          ------------------------------------------------------------

     Pursuant to the  provisions  of Section 8.1  thereof,  the Pioneer  Natural
Resources  USA, Inc.  401(k) and Matching Plan (the "Plan") is hereby amended in
the following respects only:

     FIRST:  Effective  as of  January 1,  2003,  Section  6.1(b) of the Plan is

hereby amended by adding the following two sentences to the end thereof:

     For a Participant who is a five-percent owner (as defined in Section 416(i)
     of the Code), the "required beginning date" is April 1 of the calendar year
     following  the  calendar  year such  Participant  attains age 70 1/2. For a
     Participant  who is not a five-percent  owner (as defined in Section 416(i)
     of the Code), the "required beginning date" is April 1 of the calendar year
     following the later of the calendar year in which the  Participant  attains
     age 70 1/2 or retires.

     SECOND:  Effective  as of January 1,  2003,  the Plan is hereby  amended by

adding the following new Article XI to the end thereof:

                                   ARTICLE XI.

                        MINIMUM DISTRIBUTION REQUIREMENTS

Section 1. General Rules.

     1.1. Effective Date. The provisions of this Article will apply for purposes
of determining required minimum  distributions for calendar years beginning with
the 2003 calendar year.

     1.2. Precedence. The requirements of this Article will take precedence over
any inconsistent provisions of the Plan.

     1.3. Requirements of Treasury Regulations  Incorporated.  All distributions
required under this Article will be determined  and made in accordance  with the
Treasury regulations under section 401(a)(9) of the Internal Revenue Code.

     1.4.  TEFRA  Section  242(b)(2)   Elections.   Notwithstanding   the  other
provisions of this Article,  distributions  may be made under a designation made
before January 1, 1984, in accordance  with section  242(b)(2) of the Tax Equity
and Fiscal Responsibility Act (TEFRA) and the provisions of the Plan that relate
to section 242(b)(2) of TEFRA.








Section 2. Time and Manner of Distribution.

     2.1.  Required  Beginning Date. The  Participant's  entire interest will be
distributed,  or begin to be  distributed,  to the Participant no later than the
Participant's required beginning date.

     2.2. Death of Participant  Before  Distributions  Begin. If the Participant
dies before  distributions  begin,  the  Participant's  entire  interest will be
distributed, or begin to be distributed, no later than as follows:

            (a) If the Participant's surviving  spouse is the Participant's sole
     designated  beneficiary,  then  distributions  to the surviving spouse will
     begin  by  December  31 of the  calendar  year  immediately  following  the
     calendar  year in which the  Participant  died,  or by  December  31 of the
     calendar year in which the  Participant  would have attained age 70 1/2, if
     later.

            (b) If the Participant's surviving  spouse is not the  Participant's
     sole  designated   beneficiary,   then   distributions  to  the  designated
     beneficiary  will begin by December  31 of the  calendar  year  immediately
     following the calendar year in which the Participant died.

            (c) If there is no designated beneficiary as of  September 30 of the
     year  following  the year of the  Participant's  death,  the  Participant's
     entire  interest  will be  distributed  by December 31 of the calendar year
     containing the fifth anniversary of the Participant's death.

            (d) If the Participant's surviving  spouse is the Participant's sole
     designated  beneficiary and the surviving spouse dies after the Participant
     but before  distributions to the surviving spouse begin,  this section 2.2,
     other than section 2.2(a),  will apply as if the surviving  spouse were the
     Participant.

For purposes of this section 2.2 and section 4, unless section  2.2(d)  applies,
distributions  are considered to begin on the Participant's  required  beginning
date. If section 2.2(d)  applies,  distributions  are considered to begin on the
date  distributions  are required to begin to the surviving spouse under section
2.2(a).  If distributions  under an annuity  purchased from an insurance company
irrevocably  commence  to the  Participant  before  the  Participant's  required
beginning  date  (or to the  Participant's  surviving  spouse  before  the  date
distributions  are  required  to begin to the  surviving  spouse  under  section
2.2(a)),   the  date   distributions   are  considered  to  begin  is  the  date
distributions actually commence.

     2.3.  Forms  of  Distribution.   Unless  the   Participant's   interest  is
distributed in the form of an annuity  purchased from an insurance company or in
a  single  sum on or  before  the  required  beginning  date,  as of  the  first
distribution  calendar  year  distributions  will  be made  in  accordance  with
sections 3 and 4 of this Article.  If the Participant's  interest is distributed
in the form of an annuity  purchased  from an insurance  company,  distributions
thereunder will be made in accordance with the requirements of section 401(a)(9)
of the Code and the Treasury regulations.






Section 3. Required Minimum Distributions During Participant's Lifetime.

     3.1. Amount of Required Minimum Distribution For Each Distribution Calendar
Year.  During  the  Participant's  lifetime,  the  minimum  amount  that will be
distributed for each distribution calendar year is the lesser of:

            (a) the  quotient  obtained by  dividing the  Participant's  account
     balance by the distribution  period in the Uniform Lifetime Table set forth
     in  section   1.401(a)(9)-9   of  the  Treasury   regulations,   using  the
     Participant's  age as of the  Participant's  birthday  in the  distribution
     calendar year; or

            (b)  if  the  Participant's  sole  designated  beneficiary  for  the
     distribution  calendar  year  is the  Participant's  spouse,  the  quotient
     obtained by dividing the Participant's account balance by the number in the
     Joint and Last  Survivor  Table set forth in section  1.401(a)(9)-9  of the
     Treasury regulations, using the Participant's and spouse's attained ages as
     of the  Participant's and spouse's  birthdays in the distribution  calendar
     year.

     3.2.  Lifetime  Required  Minimum  Distributions  Continue  Through Year of
Participant's  Death.  Required minimum  distributions  will be determined under
this section 3 beginning with the first distribution calendar year and up to and
including the distribution calendar year that includes the Participant's date of
death.

Section 4. Required Minimum Distributions After Participant's Death.

     4.1. Death On or After Date Distributions Begin.

            (a)  Participant  Survived   by   Designated  Beneficiary.   If  the
     Participant  dies on or after the date  distributions  begin and there is a
     designated  beneficiary,  the minimum amount that will be  distributed  for
     each distribution  calendar year after the year of the Participant's  death
     is the quotient obtained by dividing the  Participant's  account balance by
     the longer of the  remaining  life  expectancy  of the  Participant  or the
     remaining  life  expectancy of the  Participant's  designated  beneficiary,
     determined as follows:

                  (1)  The Participant's remaining life expectancy is calculated
     using the age of  the Participant in the year of death,  reduced by one for
     each subsequent year.

                  (2) If the Participant's surviving spouse is the Participant's
     sole designated beneficiary, the remaining life expectancy of the surviving
     spouse is calculated for each distribution  calendar year after the year of
     the Participant's death using the surviving spouse's age as of the spouse's
     birthday in that year.  For  distribution  calendar years after the year of
     the  surviving  spouse's  death,  the  remaining  life  expectancy  of  the
     surviving  spouse is calculated using the age of the surviving spouse as of
     the spouse's  birthday in the calendar year of the spouse's death,  reduced
     by one for each subsequent calendar year.







                  (3)  If  the  Participant's   surviving  spouse  is   not  the
     Participant's  sole designated  beneficiary,  the designated  beneficiary's
     remaining life expectancy is calculated using the age of the beneficiary in
     the year following the year of the Participant's  death, reduced by one for
     each subsequent year.

            (b) No Designated Beneficiary.  If the Participant  dies on or after
     the date distributions  begin and there is no designated  beneficiary as of
     September  30 of the year after the year of the  Participant's  death,  the
     minimum amount that will be distributed for each distribution calendar year
     after  the year of the  Participant's  death is the  quotient  obtained  by
     dividing the Participant's  account balance by the Participant's  remaining
     life expectancy  calculated using the age of the Participant in the year of
     death, reduced by one for each subsequent year.

     4.2. Death Before Date Distributions Begin.

            (a)  Participant  Survived   by  Designated   Beneficiary.   If  the
     Participant  dies  before  the  date  distributions  begin  and  there is a
     designated  beneficiary,  the minimum amount that will be  distributed  for
     each distribution  calendar year after the year of the Participant's  death
     is the quotient obtained by dividing the  Participant's  account balance by
     the remaining life expectancy of the Participant's  designated beneficiary,
     determined as provided in section 4.1.

            (b) No Designated Beneficiary.  If the  Participant dies  before the
     date  distributions  begin and  there is no  designated  beneficiary  as of
     September 30 of the year  following  the year of the  Participant's  death,
     distribution  of the  Participant's  entire  interest  will be completed by
     December 31 of the calendar year  containing  the fifth  anniversary of the
     Participant's death.

            (c) Death of  Surviving  Spouse  Before  Distributions to  Surviving
     Spouse Are  Required  to Begin.  If the  Participant  dies  before the date
     distributions   begin,   the   Participant's   surviving   spouse   is  the
     Participant's  sole designated  beneficiary,  and the surviving spouse dies
     before  distributions  are required to begin to the surviving  spouse under
     section 2.2(a), this section 4.2 will apply as if the surviving spouse were
     the Participant.

Section 5.  Definitions.

     5.1.  Designated  beneficiary.  The  individual  who is  designated  as the
beneficiary  under  Section  6.2 of the Plan and is the  designated  beneficiary
under section 401(a)(9) of the Internal Revenue Code and section  1.401(a)(9)-1,
Q&A-4, of the Treasury regulations.

     5.2.  Distribution  calendar  year.  A  calendar  year for  which a minimum
distribution is required.  For distributions  beginning before the Participant's
death,  the first  distribution  calendar year is the calendar year  immediately
preceding the calendar year which contains the Participant's  required beginning
date.  For distributions  beginning after  the  Participant's  death,  the first





distribution  calendar  year is the  calendar  year in which  distributions  are
required to begin under section 2.2. The required  minimum  distribution for the
Participant's  first  distribution  calendar  year will be made on or before the
Participant's  required  beginning date. The required  minimum  distribution for
other distribution  calendar years,  including the required minimum distribution
for the distribution calendar year in which the Participant's required beginning
date occurs, will be made on or before December 31 of that distribution calendar
year.

     5.3. Life expectancy. Life expectancy as computed by use of the Single Life
Table in section 1.401(a)(9)-9 of the Treasury regulations.

     5.4.  Participant's  account  balance.  The account  balance as of the last
valuation  date in the calendar  year  immediately  preceding  the  distribution
calendar  year  (valuation  calendar  year)  increased  by  the  amount  of  any
contributions made and allocated or forfeitures allocated to the account balance
as of  dates  in the  valuation  calendar  year  after  the  valuation  date and
decreased  by  distributions  made in the  valuation  calendar  year  after  the
valuation date. The account balance for the valuation calendar year includes any
amounts rolled over or transferred to the Plan either in the valuation  calendar
year or in the  distribution  calendar year if distributed or transferred in the
valuation calendar year.

     5.5 Required  beginning  date.  The date specified in Section 6.1(b) of the
Plan.

     IN WITNESS  WHEREOF,  this Amendment  has been executed on this 24th day of
December, 2003.

                                         PIONEER NATURAL RESOURCES USA, INC.


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