EXHIBIT 10.42

                       PIONEER NATURAL RESOURCES USA, INC.

                                  MATCHING PLAN

            (As Amended and Restated Effective as of October 1, 1997)







                       PIONEER NATURAL RESOURCES USA, INC.
                                  MATCHING PLAN

            (As Amended and Restated Effective as of October 1, 1997)

                                TABLE OF CONTENTS


                                                                           Page

PREAMBLE...................................................................  1

ARTICLE I.    DEFINITIONS AND CONSTRUCTION.................................  1
              Section 1.1  Definitions.....................................  1
              Section 1.2  Construction....................................  7

ARTICLE II.   ELIGIBILITY..................................................  7
              Section 2.1  Eligibility and Participation...................  7

ARTICLE III.  CONTRIBUTIONS, LIMITATIONS AND FORFEITURES...................  7
              Section 3.1  Matching Contributions..........................  7
              Section 3.2  Crediting of Contributions......................  8
              Section 3.3  Return of Matching Contributions................  8
              Section 3.4  Application and Allocation of Forfeitures.......  8
              Section 3.5  Rollover Contributions..........................  8
              Section 3.6  Limitations on Contributions....................  8

ARTICLE IV.   TRUST FUND................................................... 11
              Section 4.1  Trust and Trustee............................... 11
              Section 4.2  Trust Investment Options........................ 12

ARTICLE V.    VESTING...................................................... 12
              Section 5.1  Fully Vested Accounts........................... 12
              Section 5.2  Vesting of Matching Account..................... 12

ARTICLE VI.   DISTRIBUTIONS................................................ 13
              Section 6.1  Time and Form of Distribution................... 13
              Section 6.2  Distribution of Retirement Benefit.............. 14
              Section 6.3  Distribution of Death Benefit................... 15
              Section 6.4  Distribution of Separation from Employment
                      Benefit.............................................. 16
              Section 6.5  Forfeitures..................................... 16
              Section 6.6  Distributions to Minors and Persons Under Legal
                       Disability.......................................... 18

                                       (i)





              Section 6.7  Benefits Payable to Missing Participant or
                       Beneficiary......................................... 19
              Section 6.8  Transfer of Eligible Rollover Distribution...... 19
              Section 6.9  Qualified Domestic Relations Orders............. 19

ARTICLE VII.  PLAN ADMINISTRATION.......................................... 20
              Section 7.1  Matching Plan Committee......................... 20
              Section 7.2  Powers, Duties and Liabilities of the Committee. 21
              Section 7.3  Rules, Records and Reports...................... 21
              Section 7.4  Administration Expenses and Taxes............... 21

ARTICLE VIII. AMENDMENT AND TERMINATION.................................... 22
              Section 8.1  Amendment....................................... 22
              Section 8.2  Termination..................................... 22

ARTICLE IX.   TOP-HEAVY PROVISIONS......................................... 22
              Section 9.1  Top-Heavy Definitions........................... 22
              Section 9.2  Minimum Contribution Requirement................ 24

ARTICLE X.    MISCELLANEOUS GENERAL PROVISIONS............................. 24
              Section 10.1  Spendthrift Provision.......................... 24
              Section 10.2  Claims Procedure............................... 25
              Section 10.3  Maximum Contribution Limitation................ 25
              Section 10.4  Employment Noncontractual...................... 26
              Section 10.5  Limitations on Responsibility.................. 26
              Section 10.6  Merger or Consolidation........................ 26
              Section 10.7  Applicable Law................................. 26



                                      (ii)





                       PIONEER NATURAL RESOURCES USA, INC.
                                  MATCHING PLAN

            (As Amended and Restated Effective as of October 1, 1997)


     THIS MATCHING PLAN, a money purchase pension plan, made and executed by
  PIONEER NATURAL RESOURCES USA, INC., a Delaware corporation (the "Company"),

                          W I T N E S S E T H T H A T :

         WHEREAS,  the  Company has  heretofore  established  a qualified  money
purchase pension plan and trust known as the Pioneer Natural Resources USA, Inc.
Matching  Plan  (formerly  known as the Mesa  Employees  Premium  Plan and Trust
Agreement) for the benefit of certain of its employees; and

         WHEREAS,  the  Company  now  desires to  continue  said money  purchase
pension plan and trust without  interruption  by amending and restating the plan
and trust  document in its  entirety to separate  the plan and trust  provisions
into two  separate  documents,  update  the  plan  language,  incorporate  prior
amendments and make certain other changes;

         NOW,  THEREFORE,  in  consideration  of the  premises  and  pursuant to
Section 17.4 thereof, the Company hereby amends and restates the plan provisions
of said plan and trust as the Pioneer Natural Resources USA, Inc. Matching Plan,
as amended and restated effective as of October 1, 1997, to read as follows:

                                   ARTICLE I.

                          DEFINITIONS AND CONSTRUCTION

         Section  1.1  Definitions.   Unless  the   context  clearly   indicates
otherwise, when used in this Plan:


               (a)  "Account"  means  a  Participant's  Matching  Account,  Mesa
         Premium Account and/or Rollover Account, as the context requires.

               (b)  "Affiliated Company" means any corporation  or organization,
         other  than  an Employer,  which  is a  member of a controlled group of
         corporations (within  the meaning of Section 414(b) of  the Code) or of
         an  affiliated service group (within the  meaning of  Section 414(m) of
         the Code) with  respect to which an Employer  is  also  a  member,  and
         any  other  incorporated  or  unincorporated  trade or  business  which
         along with  an Employer is under common control (within the  meaning of
         the regulations from time  to time promulgated by the  Secretary of the
         Treasury  pursuant to Section 414(c) of the  Code); provided,  however,
         that for the purposes of Section 10.3 of the Plan,  Section 414 (b) and


                                      1





         (c) of the Code  shall be  applied as modified by Section 415(h) of the
         Code.

               (c)  "Code" means the Internal Revenue Code of 1986, as amended.

               (d)  "Committee" means the  Matching Plan  Committee appointed by
         the Board of Directors of the Company to administer the Plan.

               (e)  "Company"  means  Pioneer  Natural  Resources  USA,  Inc., a
         Delaware corporation, and any successor thereto.

               (f)  "Compensation"   means   the   sum  of  (i)  the  Limitation
         Compensation paid by an Employer to an Employee, (ii) any Total Pre-Tax
         Contributions  made by an Employer to the Pioneer 401(k) Plan on behalf
         of such Employee,  and (iii) any salary  reduction  amounts  elected by
         such Employee for the purchase of benefits pursuant to a cafeteria plan
         (within the  meaning of Section  125(d) of the Code)  maintained  by an
         Employer;  provided,  however,  that except for purposes of determining
         whether an Employee is a Highly Compensated  Employee or a Key Employee
         (as defined in Section  9.1(c)),  the Compensation of an Employee taken
         into account under the Plan for any Plan Year shall not exceed $150,000
         (as  adjusted  to  take  into  account  any  cost-of-living   increases
         authorized  pursuant to Section  401(a)(17)(B) of the Code). Solely for
         purposes   of  this   definition,   compensation   from   an   employer
         participating  in the Mesa Premium Plan prior to October 1, 1997, shall
         be deemed to be Compensation.

               (g)  "Covered  Employee"  means  any  Employee  other  than (i) a
         member  of  a  collective   bargaining  unit  with  which  an  Employer
         negotiates  and with  respect to whom no  coverage  under this Plan has
         been provided by collective  bargaining  agreement,  (ii) a nonresident
         alien with respect to the United  States who receives no earned  income
         from an  Employer  which  constitutes  income from  sources  within the
         United States,  (iii) a temporary or seasonal Employee as determined in
         accordance  with the  Employer's  normal  personnel  policies,  (iv) an
         individual performing services for an Employer whom the Employer treats
         as an independent  contractor  for  employment tax purposes,  or (v) an
         individual who is treated as a leased employee by an Employer.

               (h)  "Employee" means any individual employed by an Employer.

               (i)  "Employer" shall include the Company and other  incorporated
         or  unincorporated trade or business  which may subsequently adopt this
         Plan with the consent of the Board of Directors of the Company.

               (j)  "Employment Date" means the date an Employee first  performs
         an Hour of Service.



                                        2





               (k)  "Highly   Compensated   Employee"  means  for  a  Plan  Year
         commencing after December 31, 1996:

                    (1)  any  Employee  who during such Plan  Year or during the
               preceding Plan Year was at any time a 5 percent owner (as defined
               in Section  416(i)(1)  of the Code) of an  Employer or Affiliated
               Company; or

                    (2)  any  Employee  who  during  the  preceding   Plan  Year
               received Compensation greater than  $80,000 (as  adjusted to take
               into account any cost-of-living  increases authorized pursuant to
               Section 414(q)(1) of the Code) and, if the Company so elects, who
               is  in the  group  consisting of the  top 20% (when ranked on the
               basis of Compensation received during such preceding year) of all
               Employees,  except  those  excluded pursuant to Section 414(q)(5)
               of the Code.

         Solely for  purposes of this  definition,  (i) an employee of either an
         Affiliated  Company or an employer  participating  in the Mesa  Premium
         Plan shall be deemed to be an Employee, (ii) compensation received from
         either an Affiliated  Company or an employer  participating in the Mesa
         Premium  Plan  shall  be  deemed  to  be  Compensation,   and  (iii)  a
         nonresident  alien who  receives  no earned  income from an Employer or
         Affiliated  Company which  constitutes  income from sources  within the
         United States shall not be  considered  an Employee.  For the Plan Year
         ending  December  31,  1996,  Highly  Compensated  Employees  shall  be
         determined  pursuant to the provisions of the  Retirement  Savings Plan
         for Employees of Parker & Parsley as in effect for such Plan Year.

               (l)  "Hour of  Service"  means an  hour for which an  Employee is
         directly  or  indirectly   compensated  or  entitled  to   compensation
         (including  back  pay,  regardless  of  mitigation  of  damages)  by an
         Employer for the  performance  of duties for an Employer or for reasons
         (such as vacation,  sickness or disability)  other than the performance
         of duties for an  Employer.  An Employee  will be  credited  with eight
         Hours of Service per day for any  customary  work period  during  which
         such Employee is on leave of absence authorized by his or her Employer.
         Leaves of absence shall be granted by an Employer to its Employees on a
         uniform, nondiscriminatory basis. In no event shall more than 501 Hours
         of Service be  credited  on  account  of any single  continuous  period
         during which the individual  performs no duties. An Employee's Hours of
         Service shall be credited to the appropriate  Plan Years or eligibility
         computation  period  determined  in accordance  with the  provisions of
         Section  2530.200b-2(b) and (c) of the Department of Labor Regulations,
         which are incorporated  herein by this reference.  In determining Hours
         of Service for the purposes of this Plan,  periods of  employment by an
         Affiliated  Company  and  periods of  employment  as a leased  employee
         (within  the  meaning of Section  414(n) of the Code) of an Employer or
         Affiliated  Company  shall be deemed to be periods of  employment by an
         Employer.



                                        3





               (m)  "Investment   Fund"  means  any   fund  authorized  for  the
         investment of Trust assets pursuant to Section 4.2.

               (n)  "Limitation  Compensation" means wages within the meaning of
         Section  3401(a) of the Code and all other payments of  remuneration to
         an Employee by an  Employer (in  the course of  the Employer's trade or
         business)  for which the Employer is required to furnish the Employee a
         written  statement under Sections  6041(d),  6051(a)(3) and 6052 of the
         Code,  but  determined  without  regard  to any  rules  that  limit the
         remuneration  included  in wages based on the nature or location of the
         employment  or  the  services  performed  (such  as the  exception  for
         agricultural  labor  in  Section  3401(a)(2)  of the  Code);  provided,
         however,  that the  Limitation  Compensation  of an Employee taken into
         account under the Plan for any Plan Year shall not exceed  $150,000 (as
         adjusted to take into account any cost-of-living  increases  authorized
         pursuant to Section 401(a)(17)(B) of the Code).

               (o)  "Matching   Account"  means  the  account  established   and
         maintained  under this Plan by the Committee to record a  Participant's
         interest  under this Plan  attributable  to any Matching  Contributions
         made by an Employer for such Participant.

               (p)  "Matching  Contribution"  means a  contribution  made by  an
         Employer to this Plan for a Participant pursuant to Section 3.1.

               (q)  "Mesa Premium  Account" means  the  account  established and
         maintained  under this Plan by the Committee to record a  Participant's
         interest under this Plan  attributable to Employer  contributions  made
         for such  Participant  pursuant to the  provisions  of the Mesa Premium
         Plan as in effect on September 30, 1997.

               (r)  "Mesa  Premium  Plan" means the Mesa Employees  Premium Plan
         and Trust Agreement, as in effect from time to time prior to October 1,
         1997.

               (s)  "Non-Highly Compensated Employee" means for a Plan  Year any
         Employee who is not a Highly  Compensated  Employee for such Plan Year.

               (t)  The "Normal Retirement Date" of a  Participant means the day
         such Participant attains the age of 65 years.

               (u)  "One  Year Break in Service"  means a 12  consecutive  month
         Period of Severance during which an Employee fails to complete a single
         Hour of Service.

               (v)  "Participant"  means any individual who was a participant in
         the  Mesa  Premium  Plan  or any  individual  meeting  the  eligibility
         requirements  of Article II, and whose Vested  Interest under this Plan
         has not been fully distributed.



                                        4





               (w)  "Period  of  Service"  means,  for purposes of determining a
         Participant's  Vested Interest in his or her Matching Account, the sum,
         rounded  downward  to the nearest  whole  year,  of each period of time
         commencing with an Employee's  Employment Date or Reemployment Date and
         ending on the first date thereafter  that a Period of Severance  begins
         (except as provided in subsection (x) of this Section in the case of an
         Employee's  maternity or paternity leave of absence).  Included in such
         sum to be credited  to an Employee  shall be each period of time during
         which the Employee is on an authorized  leave of absence for reasons of
         vacation,  sickness,  layoff or another occasion designated and applied
         by an Employer or Affiliated Company on a nondiscriminatory  basis, but
         in no event  exceeding  one year in length.  A Period of  Service  also
         includes any Period of Severance of less than 12 consecutive months. If
         an Employee  who has no vested  right to any amount  credited to his or
         her Matching Account incurs a One Year Break in Service,  such Employee
         shall  forfeit  his or her  prior  Period of  Service  unless he or she
         completes an additional one-year Period of Service before the number of
         his or her consecutive One Year Breaks in Service equals five.

               (x)  "Period of Severance" means a period of time commencing with
         the  date  an  Employee  ceases  to  be  employed  by  an  Employer  or
         Affiliated  Company for reasons of  Retirement,  Permanent  Disability,
         death, being discharged, or voluntarily ceasing employment, or with the
         first  anniversary  of the  date of his or her  absence  for any  other
         reason,  and ending with the date such Employee resumes employment with
         an Employer or Affiliated Company;  provided,  however, that solely for
         purposes of determining  whether an Employee incurs a One Year Break in
         Service, the Period of Severance of an Employee who is absent from work
         due to the  pregnancy  of the  Employee,  the  birth  of a child of the
         Employee, the placement of a child with the Employee in connection with
         the adoption of such child by such  Employee,  or caring for such child
         for a period  beginning  immediately  following such birth or placement
         shall not commence  until the second  anniversary  of the first date of
         such absence and the period between the first and second  anniversaries
         of the first date of such absence shall be considered  neither a Period
         of Service nor a Period of Severance.

               (y)  "Permanent   Disability"  means  the  total  and   permanent
         incapacity of a  Participant  to perform the usual duties of his or her
         employment with an Employer or Affiliated  Company as determined by the
         Committee. Such incapacity shall be deemed to exist when certified by a
         physician acceptable to the Committee.

               (z)  "Pioneer  401(k)  Plan" means the Pioneer Natural  Resources
         USA, Inc. 401(k) Plan, as in effect from time to time.

               (aa) "Pioneer Pre-Tax Contributions" means  Pre-Tax Contributions
         made  by  an  Employer  to  the  Pioneer  401(k)  Plan  on  behalf of a
         Participant.



                                        5





               (bb) "Plan"  means  this  Pioneer  Natural  Resources  USA,  Inc.
         Matching Plan,  amended  and restated  effective as of October 1, 1997,
         and as from time to time in effect thereafter.

               (cc) "Plan Year" means the calendar year.

               (dd) "Qualified  Joint  and  Survivor  Annuity" means an  annuity
         which  is  payable  for the  life of the  Participant  with a  survivor
         annuity  payable for the life of his or her spouse  equal to 50% of the
         amount  of the  annuity  payable  during  the life of the  Participant;
         provided,  however,  that  in  the  case  of a  Participant  who is not
         married,  a Qualified Joint and Survivor Annuity means an annuity which
         is payable for the life of the Participant.  "Alternate Qualified Joint
         and Survivor Annuity" means an annuity which is payable for the life of
         the Participant  with a survivor annuity payable for the life of his or
         her spouse  equal to 75% or 100% of the amount of the  annuity  payable
         during the life of the Participant.

               (ee) "Qualified Preretirement Survivor  Annuity" means an annuity
         which is payable for the life of the  Participant's  surviving  spouse.

               (ff) "Reemployment   Date"  means  the  date  an  Employee  first
         performs an Hour of Service following a Period of Severance.

               (gg) "Retirement"  means   the  termination  of  a  Participant's
         employment  with an Employer or  Affiliated  Company on or after his or
         her Normal  Retirement Date for any reason other than death or transfer
         to the employment of another Employer or Affiliated Company.

               (hh) "Rollover   Account"  means  the  account  established   and
         maintained  under this Plan by the Committee to record a  Participant's
         interest  under  this  Plan   attributable  to  (i)  Rollover  Property
         contributed  by such  Participant  to this Plan pursuant to Section 3.5
         and (i) any amounts  credited to his or her Rollover  Account under the
         Mesa Premium Plan as in effect on September 30, 1997.

               (ii) "Rollover  Property" means property the value of which would
         be excluded from the  gross  income  of the  transferor  under  Section
         402(c), 403(a)(4) or 408(d)(3) of the Code if transferred to the Plan.

               (jj) "Trust" means the trust fund established pursuant to Section
         4.1.

               (kk) "Trustee"  means the  individual  or  corporate  trustee  or
         trustees from time to time  appointed and acting as trustee or trustees
         of the Trust established pursuant to the Plan.



                                        6





               (ll) "Valuation Date" means each business day.

               (mm) The  "Vested  Interest"  of a  Participant  means  the  then
         vested  portion  of  the  amount  credited  to  the  Accounts  of  such
         Participant at the particular point in time in question.

         Section 1.2  Construction.  The titles to the Articles and the headings
of the Sections in this Plan are placed herein for convenience of reference only
and in case of any conflict the text of this instrument, rather than such titles
or headings,  shall control.  Whenever a noun or pronoun is used in this Plan in
plural form and there be only one person or entity  within the scope of the word
so used,  or in singular form and there be more than one person or entity within
the  scope of the word so used,  such  noun or  pronoun  shall  have a plural or
singular meaning as appropriate under the circumstance.


                                   ARTICLE II.

                          ELIGIBILITY AND PARTICIPATION

         Section 2.1  Eligibility and Participation.  Each Covered  Employee who
is a participant  in the Mesa Premium Plan on September 30, 1997 shall  continue
to be a  Participant  in the Plan as of  October 1,  1997.  Each  other  Covered
Employee  shall become a Participant  in this Plan on the first day of the first
pay period in the  calendar  month next  following  his or her  employment  as a
Covered  Employee.  Any  Participant  who ceases to be a Covered  Employee shall
thereupon cease to participate in the Plan; provided,  however, that if any such
Participant  is  thereafter  reemployed as a Covered  Employee,  he or she shall
resume participation in the Plan as of the date of such reemployment.

                                  ARTICLE III.

                   CONTRIBUTIONS, LIMITATIONS AND FORFEITURES

         Section  3.1  Matching  Contributions.  For each pay period an Employer
shall make to the Plan for each  Participant  in its employ and allocate to such
Participant's  Matching  Account  a  contribution  equal to 200  percent  of the
Pioneer Pre-Tax  Contributions made by the Employer on such Participant's behalf
during  such  pay  period  which  are  not in  excess  of five  percent  of such
Participant's  Basic  Compensation  (as defined in the Pioneer  401(k) Plan) for
such pay period.  The  Matching  Contributions  to be made to the Plan for a pay
period shall be paid to the Trustee as soon as practicable, but no later than 30
days after the end of the month in which such pay period ends.



                                        7





         Section 3.2  Crediting of Contributions.  The Committee shall establish
and maintain a Matching Account for each Participant. All Matching Contributions
made for a Participant shall be credited to such Participant's Matching Account.

         Section 3.3  Return of  Matching  Contributions.  Contributions made to
this Plan are conditioned  upon being currently  deductible under Section 404 of
the Code.  Any provision of this Plan to the contrary  notwithstanding,  upon an
Employer's  request,  any such contribution or portion thereof made to this Plan
by such  Employer  which  (i)  was  made  under  a  mistake  of  fact  which  is
subsequently  discovered or (ii) is disallowed as a deduction  under Section 404
of the Code,  shall be  returned to such  Employer to the extent not  previously
distributed to Participants or their beneficiaries;  provided, however, that the
amounts  returnable to an Employer  pursuant to this Section shall be reduced by
any Trust losses  allocable  thereto and shall be returned to such Employer only
if such  return is made  within  one year  after  the  mistaken  payment  of the
contribution or the date of the  disallowance of the deduction,  as the case may
be.  Except as provided in this  Section,  no  contribution  made by an Employer
pursuant to this Plan shall ever revert to or be recoverable by any Employer.

         Section 3.4  Application  and  Allocation of  Forfeitures.  All amounts
forfeited  during a Plan Year shall  first be applied to restore  any  forfeited
Matching Account  required to be restored  pursuant to Sections 6.5 and 6.7, and
any forfeitures in excess of the amount needed to restore any such Account shall
be used to reduce the amount of the earliest subsequent  Matching  Contributions
the Employer otherwise would be required to make to the Plan.

         Section 3.5  Rollover Contributions. With the consent of the Committee,
any Covered  Employee  (regardless  of whether he or she is a  Participant)  may
contribute  Rollover Property in the form of cash to the Plan. Each contribution
of Rollover  Property  shall be credited  to a separate  Rollover  Account to be
established  and maintained  for the benefit of the  contributing  Employee.  An
Employee  who is not a  Participant,  but for whom a  Rollover  Account is being
maintained,  shall be accorded all of the rights and privileges of a Participant
under  the Plan  except  that no  contributions  (other  than  contributions  of
Rollover  Property)  shall be made for such  Employee  until he or she meets the
eligibility and participation requirements of Section 2.1.

         Section 3.6  Limitations on Contributions.

               (a)  Any provision of this Plan to the contrary  notwithstanding,
         if for any  Plan  Year  the  contribution  percentage for the  group of
         Highly  Compensated  Employees  eligible  to  receive an allocation  of
         Matching  Contributions  for such Plan Year fails to satisfy one of the
         following tests:

                    (1)  the contribution  percentage for  said  group of Highly
               Compensated   Employees  is  not   more   than  1.25  times   the
               contribution   percentage   for the preceding   Plan Year for all
               


                                        8





               Non-Highly Compensated Employees eligible for the  preceding Plan
               Year to receive an allocation of Matching Contributions, or

                    (2) the excess of the contribution percentage for said group
               of Highly Compensated Employees over the contribution  percentage
               for  the  preceding Plan for all Non-Highly Compensated Employees
               eligible for the preceding Plan Year to receive an allocation  of
               Matching  Contributions is not more than  two percentage  points,
               and  the  contribution   percentage  for  said  group  of  Highly
               Compensated Employees is not more than two times the contribution
               percentage  for  the  preceding  Plan  Year  for  all  Non-Highly
               Compensated  Employees eligible for the preceding  Plan  Year  to
               receive an allocation of Matching Contributions,

         then the  contribution  percentage for  Participants who are members of
         said group of Highly Compensated Employees shall be reduced by reducing
         the  Matching  Contributions  made for such  Plan  Year for the  Highly
         Compensated   Employees  with  the  largest   individual   contribution
         percentages to the largest uniform contribution  percentage (commencing
         with the Highly  Compensated  Employee  with the  largest  contribution
         percentage  and  reducing  his or her  contribution  percentage  to the
         extent  necessary  to satisfy  one of the above  tests or to lower such
         contribution  percentage to the  contribution  percentage of the Highly
         Compensated Employee with the next highest contribution percentage, and
         repeating  this process as  necessary)  that  permits the  contribution
         percentage  for said group of Highly  Compensated  Employees to satisfy
         one of said  tests.  For  purposes  of this  subsection  (a),  the term
         "contribution percentage" for a specified group of Employees for a Plan
         Year means the average of the ratios  (calculated  separately  for each
         Employee  in such  group and after  application  of the  reduction  and
         forfeiture  provisions of Sections 3.4(a) and (b) of the Pioneer 401(k)
         Plan) of (i) the aggregate amount of Matching Contributions made to the
         Plan for each such  Employee  for that year and, at the election of the
         Committee,  all or a portion of the Total Pre-Tax Contributions made on
         behalf of such Employee to the Pioneer  401(k) Plan for that year which
         are  not in  excess  of the  amount  of  such  contributions  that  are
         permitted to be taken into account under Sections 401(k) and (m) of the
         Code  and the  regulations  thereunder,  to  (ii)  the  amount  of such
         Employee's   Compensation   for  that  year  or,  in  the   Committee's
         discretion,  only  for such  portion  of that  year  during  which  the
         Employee was eligible to participate in the Plan. Any provision of this
         Section  to the  contrary  notwithstanding,  for the Plan  Year  ending
         December 31, 1997,  the Company may elect,  in accordance  with Section
         401(m) of the Code and other applicable authority,  to use data for the
         current Plan Year rather than the preceding  Plan Year in computing the
         contribution  percentage of Non-Highly Compensated Employees. If two or
         more  plans to  which  matching  contributions  or  employee  after-tax
         contributions  are made are  considered  as one  plan for  purposes  of
         Section  410(b) of the Code  (other  than for  purposes  of the average
         benefit  percentage  test), such plans shall be treated as one plan for
         purposes   of  determining  the  contribution   percentages  for   this

                                        9





         subsection  (a). If a Highly Compensated Employee is  a  participant in
         two or more plans to which matching contributions or employee after-tax
         contributions   are  made,  then  for   purposes  of   determining  the
         contribution  ratio of such Employee,  all such plans (other than those
         that may not be permissively aggregated) shall be treated as one plan.

               (b)  The aggregate  amount of any Matching Contributions made for
         Participants  which  cannot be credited  to the Matching Accounts for a
         Plan Year  because  of the  limitation  contained in subsection  (a) of
         this Section (along with any income allocable to such contributions for
         such Plan Year,  but not for the gap period  following  such Plan Year)
         shall be forfeited if forfeitable, but if not forfeitable,  distributed
         to such  Participants  no later than 2 1/2 months after the end of such
         year on the basis of the amount of Matching Contributions made for each
         such Participant  (commencing with the Highly Compensated Employee with
         the  largest  amount of Matching  Contributions  for such Plan Year and
         reducing his or her Matching  Contributions  to the extent necessary or
         to lower such  amount to the amount of  Matching  Contributions  of the
         Highly  Compensated  Employee with the next highest  amount of Matching
         Contributions,  and repeating  this process as  necessary).  The income
         allocable to any such excess aggregate  contributions for a Participant
         for a Plan Year shall be determined by multiplying the amount of income
         allocable  to such  Participant's  Matching  Account for such year by a
         fraction,  the numerator of which is the amount of the excess aggregate
         contributions  for such year and the denominator of which is the sum of
         the amount credited to such  Participant's  Matching  Account as of the
         beginning  of such year plus the amount of the  Matching  Contributions
         made for such Participant for such year.

               (c)  Any provision of this Plan to the contrary  notwithstanding,
         in addition to the above limitations of this Section, the  sum  of  the
         actual  deferral  percentage  and  the  contribution percentage for the
         group of Highly  Compensated  Employees  as  determined pursuant to and
         after any  reduction  in such percentages required by subsection (a) of
         this Section and  Section 3.4(a) of the  Pioneer 401(k)  Plan shall not
         exceed the  "aggregate  limit."  The  "aggregate  limit" shall be equal
         to the greater of:

                         (1)  the sum of:  (i) 1.25 times  the  greater  of  the
               relevant actual deferral percentage or the  relevant contribution
               percentage, and (ii) two percentage points plus the lesser of the
               relevant actual  deferral percentage or the relevant contribution
               percentage,  provided that the  amount in this  clause (ii) shall
               not exceed two times the lesser of the relevant  actual  deferral
               percentage or the relevant contribution percentage; or

                         (2)  the sum of:  (i) 1.25  times  the  lesser  of  the
               relevant actual deferral percentage or the relevant  contribution
               percentage,   and (ii) two  percentage points plus the greater of
               the   relevant  actual   deferral   percentage  or  the  relevant
               contribution percentage,  provided that the amount in this clause
               


                                       10





               (ii) shall  not  exceed  two  times  the  greater of the relevant
               actual  deferral   percentage   or   the  relevant   contribution
               percentage.

         The "relevant  actual  deferral  percentage"  means the actual deferral
         percentage  determined  for the preceding Plan Year pursuant to Section
         3.4(a)  of  the  Pioneer  401(k)  Plan  for  the  group  of  Non-Highly
         Compensated  Employees  eligible during the preceding Plan Year to have
         Pre-Tax  Contributions  or  Pre-Tax  Bonus  Contributions  made  to the
         Pioneer 401(k) Plan. The "relevant  contribution  percentage" means the
         contribution percentage determined for the preceding Plan Year pursuant
         to  subsection  (a)  of  this  Section  for  the  group  of  Non-Highly
         Compensated  Employees  eligible for the preceding Plan Year to receive
         an  allocation  of  Matching  Contributions.  In  the  event  that  the
         aggregate  limit is  exceeded  in any year,  then the  actual  deferral
         percentage under the Pioneer 401(k) Plan and/or contribution percentage
         under this Plan for Participants who are members of the group of Highly
         Compensated  Employees  shall be  reduced  by  reducing  Total  Pre-Tax
         Contributions   to  the  Pioneer   401(k)  Plan  and/or  any   Matching
         Contributions  made for such Plan  Year for or on behalf of the  Highly
         Compensated  Employees  with the  largest  individual  actual  deferral
         percentages  and/or  contribution  percentages  to the largest  uniform
         actual deferral percentage and/or contribution  percentage  (proceeding
         in the manner  prescribed in Section  3.4(a) of the Pioneer 401(k) Plan
         and  subsection (a) of this Section) that permits the sum of the actual
         deferral  percentage  and  contribution  percentage  for said  group of
         Highly  Compensated  Employees to satisfy the above  restrictions.  The
         provisions of  subsection  (b) of this Section shall apply with respect
         to any  Matching  Contributions  which  cannot be  credited to Matching
         Accounts  under this Plan because of the  limitation  contained in this
         subsection (c).

               (d)  If  any  portion  of  a   Pioneer  Pre-Tax  Contribution  is
         distributed to a Participant  pursuant to Section 3.4(b) of the Pioneer
         401(k)  Plan,  any portion of a Matching  Contribution  (along with any
         income  allocable  thereto) made to this Plan for such Participant that
         corresponds to such distributed  Pioneer Pre-Tax  Contribution shall be
         forfeited.


                                   ARTICLE IV.

                  TRUST FUND, INVESTMENT OPTIONS AND VALUATIONS

         Section 4.1  Trust and  Trustee.  All of the contributions  paid to the
Trustee  pursuant  to this Plan and the Mesa  Premium  Plan,  together  with the
income  therefrom  and the  increments  thereof,  shall  be held in trust by the
Trustee under the terms and provisions of the separate trust  agreement  between
the Trustee and the Company, a copy of which is attached hereto and incorporated
herein by this  reference for all purposes,  establishing  a trust fund known as



                                       11





the PIONEER NATURAL RESOURCES USA, INC. MATCHING TRUST for the exclusive benefit
of the Participants and their beneficiaries.

         Section 4.2  Trust Investment  Options.  For investment  purposes,  the
trust fund  established  under the Trust  shall be divided  into such number and
kind of separate and distinct  Investment Funds as the Committee in its absolute
discretion  shall authorize from time to time. The assets of the Trust allocated
to a particular  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  agreement  establishing  the  Trust,  as the case may be, in such type of
property  acceptable  to the  Trustee as the  Trustee is directed to acquire and
hold for such  Investment  Fund.  Upon becoming a Participant in the Plan,  each
Participant  shall  direct,  in the manner  prescribed  by the  Committee in its
absolute discretion,  that all amounts credited to his or her Accounts under the
Plan shall be invested, in percentage multiples authorized by the Committee,  in
one or more of the Investment Funds.  Subject to such conditions and limitations
as the Committee in its absolute  discretion may prescribe from time to time for
application to all Participants on a uniform basis, a Participant may change his
or her investment direction with respect to future contributions or redirect the
investment of amounts  credited to his or her Accounts,  provided that notice of
such change is delivered to or in the manner  directed by the  Committee  within
such  reasonable  period of time  prior to the  effective  date  thereof  as the
Committee may require.

         Section 4.3  Valuation and Adjustment of Accounts. As of each Valuation
Date,  the Trustee  shall  determine  the fair market value of all assets of the
Trust with the value of the  assets of each  Investment  Fund  being  separately
determined.  On the  basis  of  such  valuations  and in  accordance  with  such
procedures as may be specified from time to time by the  Committee,  the portion
of each Account  invested in a particular  Investment  Fund shall be adjusted by
the  Committee to reflect its  proportionate  share of the income  collected and
accrued,  realized  and  unrealized  profits and losses,  expenses and all other
transactions  attributable to that particular  Investment Fund for the valuation
period then ended. The amount of any distribution forfeiture shall be determined
on the basis of the most recent valuation  preceding the date of distribution or
forfeiture, as the case may be.


                                   ARTICLE V.

                                     VESTING

         Section  5.1  Fully  Vested   Accounts.   The  amounts  credited  to  a
Participant's  Mesa Account and Rollover  Account (if any) shall be fully vested
at all times.

         Section 5.2  Vesting of Matching Account.  The amounts  credited to the
Matching Account of a Participant  shall become fully vested upon the occurrence
of any of the following  events while the Participant is in the employ of (or on



                                       12





authorized  leave of absence  from) an Employer or Affiliated  Company:  (i) the
completion of an Hour of Service by the  Participant  on or after the date he or
she attains age 60, (ii) the  Participant's  death,  or (iii) the  Participant's
Permanent  Disability.  Unless sooner vested pursuant to the preceding sentence,
the  amounts  credited  to  a  Participant's  Matching  Account  shall  vest  in
accordance with the following schedule:

            Period of Service
         Completed by Participant               Percentage Vested
         ------------------------               -----------------

            Less than 1 year                           None
            1 year                                      25%
            2 years                                     50%
            3 years                                     75%
            4 or more years                            100%


                                   ARTICLE VI.

                                  DISTRIBUTIONS

         Section  6.1  Time  and  Form  of   Distribution.   Distribution  to  a
Participant  or  beneficiary  under this Article shall be made or commence being
made no later  than 60 days after the close of the Plan Year in which the latest
of the following occurs: (i) the Participant's  Normal Retirement Date, (ii) the
tenth anniversary of the year in which the Participant  commenced  participation
in the Plan, or (iii) the  Participant's  separation  from the  employment of an
Employer  for any reason  other than his or her  transfer to the  employment  of
another  Employer or Affiliated  Company.  In addition and any provision of this
Plan to the  contrary  notwithstanding,  in the case of a  Participant  who is a
five-percent owner (as defined in Section 416(i) of the Code) or at the election
of any other  Participant  who  attains  age 70 1/2 prior to  January  1,  1999,
distribution to such Participant  under the Plan shall be made or commence being
made no later than April 1 of the calendar  year  following the calendar year in
which the Participant attains age 70 1/2. Distributions that commence being made
pursuant to the preceding  sentence to a Participant  who has not separated from
the  employment of an Employer or  Affiliated  Company shall be made pursuant to
Section 6.2 as if the  Participant  had  terminated  employment at such time and
shall  be made in  accordance  with the  minimum  distribution  requirements  of
Section 401(a)(9) of the Code and the regulations thereunder; provided, however,
that if a Participant  elects to waive payment in the form of a Qualified  Joint
and Survivor  Annuity in accordance  with Section 6.2, the  alternative  form of
distribution  shall be payment of the minimum amounts required to be distributed
pursuant to Section  401(a)(9) of the Code and the regulations  thereunder,  but
without recalculation of life expectancy, and with any amount remaining upon the
termination  of the  Participant's  employment or death to be paid in accordance
with Section 6.2 or Section 6.3, whichever is applicable,  but with any payments



                                       13





adjusted or  accelerated  as  necessary to satisfy the  requirements  of Section
401(a)(9) of the Code and the regulations thereunder.  Subject to the provisions
of this Article  requiring that  distributions be made in the form of an annuity
contract, distributions shall be made in cash. Any provision of this Plan to the
contrary  notwithstanding,  (A) all distributions from the Plan shall be made in
accordance with Section  401(a)(9) of the Code and the  regulations  thereunder,
and (B) all optional  forms of benefit  under the Plan and the Mesa Premium Plan
that are protected  benefits under Section  411(d)(6) of the Code shall continue
to be optional forms of benefit for  Participants to whom such optional forms of
benefit apply  notwithstanding any subsequent  amendment purporting to revise or
delete any such optional form of benefit.

         Section 6.2  Distribution of Retirement Benefit.

               (a)  Except  as  otherwise  provided in this  Section,  upon  the
         Retirement  or  Permanent  Disability  of  a  Participant,  the  Vested
         Interest of such  Participant  shall be distributed to such Participant
         by the  Trustee  at the  direction  of the  Committee  in the form of a
         Qualified  Joint and Survivor  Annuity  contract to be purchased from a
         company  selected by the Committee and commencing in payment as soon as
         practicable  unless the  Participant's  Vested Interest does not exceed
         $3,500 ($5,000  commencing  January 1, 1998), in which event it will be
         distributed to the Participant as soon as practicable  following his or
         her  Retirement  or  Permanent  Disability  in  the  form  of a  single
         distribution.   No  distribution  shall  be  made  upon  the  Permanent
         Disability of a Participant  prior to his or her Normal Retirement Date
         unless such Participant  consents to receive such  distribution or such
         Participant's Vested Interest does not exceed $3,500 ($5,000 commencing
         January 1, 1998).

               (b)  At least 30 days but not more than 90 days prior to the date
         the Qualified Joint and  Survivor  Annuity  contract  is to commence in
         payment to a Participant, the Committee shall  provide such Participant
         with a  written  explanation  of (i)  the terms  and conditions of  the
         Qualified Joint  and Survivor  Annuity,  (ii) his or her right to make,
         and  the  effect of, an  election to  waive  the  Qualified  Joint  and
         Survivor Annuity form of benefit, (iii) the rights of his or her spouse
         with  respect  to the  receipt  and waiver of the  Qualified  Joint and
         Survivor  Annuity,  and (iv) the right to make,  and the  effect  of, a
         revocation  of an election to waive the  Qualified  Joint and  Survivor
         Annuity.

               (c)  After receiving the  explanation described in (b) above, the
         Participant  may elect at  any  time during the 90-day period ending on
         the date the  annuity contract is to  commence in  payment to waive the
         Qualified  Joint and  Survivor  Annuity  form of  benefit  and also may
         revoke any such election during such period. Any such election to waive
         a Qualified  Joint and  Survivor  Annuity  form of benefit by a married
         Participant  will be effective  only if the spouse of such  Participant
         consents  in  writing  within  the 90- day  period  preceding  both the
         election and the optional form of benefit  selected by the  Participant
         and such consent is witnessed by a member of the  Committee or a notary
         public.


                                       14





               (d)  Any amount  payable  under the Plan  upon the  Retirement or
         Permanent  Disability  of a  Participant  who has  elected to waive the
         Qualified Joint and Survivor  Annuity form of benefit as provided above
         shall  be  distributed  to  such  Participant  by  the  Trustee  at the
         direction of the Committee in one of the following forms to be selected
         by the Participant:

               (i)  by payment of the entire amount in a single distribution;

                    (by payment of the entire amount in monthly,  quarterly,  or
                    annual installments over a specifically designated period of
                    time over a period of two  or more years, but not to  exceed
                    one or a combination of the  following periods: (i) the life
                    of  the  Participant,  (ii) the  lives  of  the  Participant
                    and  his  or  her  designated   beneficiary,  (iii) a period
                    certain not extending beyond  the  life  expectancy  of  the
                    Participant,  and (iv) a period certain not extending beyond
                    the  joint  life  and   last   survivor  expectancy  of  the
                    Participant and his or her designated beneficiary,  provided
                    that if a  Participant  who elects installment payments dies
                    prior to the distribution of the entire amount of his or her
                    vested interest, the  remaining  portion  thereof  shall  be
                    distributed  to  his  or  her  beneficiary or  beneficiaries
                    (determined in accordance  with  Section 6.3)  in  a  single
                    distribution; or

               (ii) by purchase  of  an  Alternate  Qualified Joint and Survivor
                    Annuity contract from a company selected by the Committee;

         provided,  however,  that the  consent of the  Participant's  spouse as
         provided above shall not be required if the Participant selects payment
         in the form of an Alternate Qualified Joint and Survivor Annuity.

               (e)  Distributions  pursuant to this  Section 6.2 shall  be  made
         or commence being made as soon as practicable but no later than 60 days
         following  the close of the Plan Year in which the event giving rise to
         a distribution occurred.

         Section 6.3  Distribution of Death Benefit.

               (a)  Except as  otherwise  provided  in this  Section,  upon  the
         death of a  Participant  who is  married,  the Vested  Interest of such
         Participant shall be distributed by the Trustee at the direction of the
         Committee  to his or her  surviving  spouse in the form of a  Qualified
         Preretirement  Survivor Annuity contract to be purchased from a company
         selected  by the  Committee  and  commencing  in  payment  as  soon  as
         practicable following the Participant's death.



                                       15





               (b)  The Committee shall provide  each such  married  Participant
         with a written  explanation  of the  Qualified  Preretirement  Survivor
         Annuity provided above,  including the Participant's right to waive the
         distribution of such Qualified  Preretirement Survivor Annuity with the
         consent  of his or her spouse  and to revoke  any such  waiver,  within
         whichever of the following  periods ends last: (i) the period beginning
         with the first day of the Plan  Year in which the  Participant  attains
         the age of 32 and ending with the close of the Plan Year  preceding the
         Plan  Year in which the  Participant  attains  the age of 35,  (ii) the
         one-year  period after the individual  becomes a Participant,  or (iii)
         the one-year  period after  separation from employment in the case of a
         Participant who separates before attaining age 35.

               (c)  Each  married  Participant  may elect  at  any time prior to
         such Participant's death to waive the Qualified  Preretirement Survivor
         Annuity  form of  benefit  provided  above  so that  his or her  entire
         benefit may be paid to his or her designated  beneficiary.  No election
         to waive the Qualified Preretirement Survivor Annuity will be effective
         upon  the  Participant's   death  unless  such  election  designates  a
         beneficiary  that  cannot  be  changed  without  spousal  consent,  the
         Participant's surviving spouse consents in writing to such election and
         such  consent is  witnessed  by a member of the  Committee  or a notary
         public. A married Participant may revoke any such election to waive the
         Qualified  Preretirement  Survivor  Annuity at any time prior to his or
         her death.

               (d)  The  amount  payable  under  the  Plan  upon  the death of a
         married  Participant  who has elected,  as provided above, to waive the
         Qualified   Preretirement   Survivor   Annuity  and  has  designated  a
         beneficiary, shall be distributed to the beneficiary designated by such
         Participant.  Such  designation  shall  be  made in  writing  on a form
         prescribed by the Committee and, when filed with the  Committee,  shall
         become  effective and remain in effect until changed by the Participant
         by the filing of a new beneficiary designation form with the Committee.
         If an unmarried Participant fails to so designate a beneficiary,  or in
         the  event  all  of  a  Participant's   designated   beneficiaries  are
         individuals who predecease such  Participant,  then the Committee shall
         direct the Trustee to distribute  the amount  payable under the Plan to
         such  Participant's  surviving  spouse,  if any,  but if none,  to such
         Participant's estate.

               (e)  All  distributions   under  this  Section,  other  than  the
         Qualified  Preretirement Survivor Annuity provided above, shall be made
         in  a  single   distribution   as  soon  as  practicable   following  a
         Participant's death;  provided,  however,  that a Participant may elect
         (or  if  the  Participant   does  not  elect,  his  or  her  designated
         beneficiary may elect) that distribution be made in monthly,  quarterly
         or annual  installments  over a period of two or more years, but not to
         exceed one or a combination of the following  periods:  (i) the life of
         the Participant's designated beneficiary,  or (ii) a period certain not
         extending  beyond the life expectancy of the  Participant's  designated
         beneficiary.



                                       16





               (f)  Distributions made pursuant to this  Section 6.3 in the form
         a Qualified  Preretirement Survivor  Annuity contract shall be made and
         such contract  shall provide for  commencement of payment no later than
         one  year  after  the  Participant's death. Distributions made pursuant
         to  this  Section  6.3 in any  other  form  shall  be made or  commence
         being made as soon as  practicable  but no later than 90 days following
         the close of the Plan Year in which the Participant's death occurs.

               (g)  Any   provision   of   this  Section  6.3  to  the  contrary
         notwithstanding,  the surviving spouse of any deceased  Participant may
         elect in writing after the Participant's  death to receive the benefits
         otherwise payable to such surviving spouse in one of the forms provided
         in Section  6.3(e)  above or in the form of a  Qualified  Preretirement
         Survivor  Annuity  commencing  in  payment as of such later date as the
         surviving  spouse  may  elect,   provided  that  such  delayed  payment
         commencement  date complies with the provisions of Section 401(a)(9) of
         the Code and the regulations thereunder.

         Section 6.4  Distribution of Separation from Employment  Benefit.  If a
Participant  separates from the employment of an Employer or Affiliated  Company
for any reason other than his or her Retirement,  Permanent Disability, death or
transfer to the  employment  of another  Employer  or  Affiliated  Company,  the
Accounts of such Participant shall be retained in trust and shall continue to be
credited  with  applicable  earnings as provided in Section  4.3, and the Vested
Interest of such  Participant  shall be distributed  to such  Participant by the
Trustee  at the  direction  of the  Committee  upon  such  Participant's  Normal
Retirement Date by payment of the entire amount in the form of a Qualified Joint
and Survivor  Annuity  contract to be purchased  from a company  selected by the
Committee and  commencing in payment as soon as practicable  thereafter  (or, if
the  Participant  dies prior to his or her Normal  Retirement  Date,  the Vested
Interest of such Participant under the Plan shall be distributed upon his or her
death in accordance  with Section 6.3);  provided,  however,  that (i) each such
Participant shall have the right to receive an early  distribution of his or her
Vested  Interest  under the Plan in the form of a Qualified  Joint and  Survivor
Annuity  contract to be purchased  from a company  selected by the Committee and
commencing in payment as soon as practicable  following  such election,  or upon
satisfaction of the notice and waiver  requirements of Section 6.2, in any other
form provided for  distributions  upon  Retirement  pursuant to Section 6.2, and
(ii) the  Committee  shall  require  an early  distribution  in cash of any such
Participant's  Vested  Interest which does not exceed $3,500 ($5,000  commencing
January 1, 1998).

         Section 6.5  Forfeitures.

               (a)  Unless sooner  forfeited  as provided  below,  any  unvested
         portion of the Matching Account of a Participant who separates from the
         employment  of an Employer or  Affiliated  Company for any reason other
         than his or her Retirement,  Permanent Disability, death or transfer to
         the  employment  of another  Employer or  Affiliated  Company  shall be
         forfeited upon the earlier of the date of such  Participant's  death or
         the date such  Participant  incurs five  consecutive One Year Breaks in
         


                                       17





         Service  unless  such  Participant is  reemployed  by  an  Employer  or
         Affiliated Company prior to such date.

               (b)  If a  Participant  receives a  distribution  of  his or  her
         Vested  Interest by the end of the second Plan Year  following the year
         in which his or her separation from  employment  occurred under Section
         6.4, any portion of such  Participant's  Matching  Account which is not
         vested  at the time of such  distribution  shall be  forfeited  at such
         time. If a Participant who separates from the employment of an Employer
         or Affiliated  Company for any reason other than his or her Retirement,
         Permanent  Disability,  death or transfer to the  employment of another
         Employer  or  Affiliated  Company,  is  not  entitled  to  receive  any
         distribution from the Plan due to the fact that such Participant has no
         Vested Interest,  such  Participant  shall be deemed to have received a
         distribution  from the Plan of his or her entire Vested  Interest under
         the Plan and any amount credited to such Participant's Matching Account
         shall be forfeited at the time of such separation from employment. If a
         Participant any portion of whose Matching Account is forfeited pursuant
         to this  subsection  (b) is reemployed as a Covered  Employee  prior to
         incurring five  consecutive  One Year Breaks in Service,  the amount so
         forfeited shall be restored to such  individual's  Matching Account out
         of current-year  forfeitures or, if such forfeitures are  insufficient,
         by an additional Employer contribution.

               (c)  If a  Participant  who has not yet incurred five consecutive
         One Year Breaks in Service  receives a  distribution  under Section 6.4
         after the end of the second Plan Year  following  the year in which his
         or her  separation  from  employment  occurred,  any  portion  of  such
         Participant's  Matching Account which is not vested at the time of such
         distribution  shall be retained in such  Account and shall be forfeited
         upon the  earlier of the date of such  Participant's  death or the date
         such  Participant  incurs five  consecutive  One Year Breaks in Service
         unless such  Participant  is  reemployed  by an Employer or  Affiliated
         Company prior to such date. If a  Participant  receives a  distribution
         from the Plan after the end of the second Plan Year  following the year
         in  which  his  or  her  separation  from  employment  occurred  and is
         reemployed by an Employer or Affiliated Company prior to incurring five
         consecutive  One Year Breaks in Service,  then the unvested  balance in
         his or her  Matching  Account  shall  be  transferred  to a  segregated
         account for such  Participant  and the amount that the  Participant  is
         entitled to receive from such  segregated  account as of any later date
         shall be an amount  equal to X, which  amount  shall be  determined  in
         accordance  with the following formula:  X = P (AB + D) - D, where P is
         the  Participant's  vested  percentage  at such later  date,  AB is the
         amount in his or her  segregated  account at such later date,  and D is
         the amount distributed to the Participant in connection with his or her
         earlier separation from employment.

         Section 6.6  Distributions  to   Minors   and   Persons   Under   Legal
Disability.  If any  distribution  under the Plan becomes  payable to a minor or



                                       18





other person under a legal disability,  such  distribution  shall be made to the
duly  appointed  guardian  or other legal  representative  of the estate of such
minor or person under legal disability.

         Section 6.7  Benefits Payable to Missing Participant or Beneficiary. If
the  Committee  cannot  locate  a  Participant  or  beneficiary  entitled  to  a
distribution  under  this  Plan  within  a  period  of three  years  after  such
Participant or beneficiary  becomes  entitled to the  distribution,  the amounts
credited to the Accounts of such Participant or beneficiary  shall be forfeited;
provided,   however,  that  if  a  claim  for  any  such  forfeited  amounts  is
subsequently  made by any person  entitled to the  distribution,  such forfeited
amounts shall be restored (without  adjustment for earnings or appreciation) out
of current-year  forfeitures,  or if such  forfeitures are  insufficient,  by an
additional Employer contribution.

         Section  6.8  Transfer  of  Eligible   Rollover   Distribution.   If  a
Participant is entitled to receive an eligible rollover distribution (as defined
in Section  402(c) of the Code and the  regulations  thereunder)  from the Plan,
such  Participant may elect to have the Committee direct the Trustee to transfer
the  entire  amount  of  such  distribution  directly  to any  of the  following
specified by such  Participant:  an individual  retirement  account described in
Section  408(a) of the Code,  an  individual  retirement  annuity  described  in
Section  408(b)  of the Code  (other  than an  endowment  contract),  a  defined
contribution  plan qualified under Section 401(a) of the Code the terms of which
permit rollover  contributions or an annuity plan described in Section 403(a) of
the Code.  If the  surviving  spouse of a deceased  Participant  is  entitled to
receive an eligible  rollover  distribution from the Plan, such surviving spouse
may elect to have the Committee direct the Trustee to transfer the entire amount
of such  distribution  directly  to  either  an  individual  retirement  account
described  in Section  408(a) of the Code or an  individual  retirement  annuity
described  in Section  408(b) of the Code  (other  than an  endowment  contract)
specified by such  surviving  spouse.  If an  alternate  payee under a qualified
domestic  relations  order (as  defined  in  Section  414(p) of the Code) is the
spouse or former spouse of the Participant  specified in the qualified  domestic
relations  order,  this Section  shall apply to such  alternate  payee as if the
alternate  payee were a  Participant.  A  distributee  of an  eligible  rollover
distribution  who is entitled to make an election under this Section may specify
that  some  portion  less  than  the  entire  amount  of  such  distribution  be
transferred in accordance with this Section.

          Section 6.9  Qualified  Domestic  Relations  Orders.  Any provision of
this Plan to the contrary notwithstanding:

               (a)  The  Committee   shall  establish  and  maintain   for  each
         alternate  payee named with respect to a  Participant  under a domestic
         relations  order which is determined by the Committee to be a qualified
         domestic  relations  order (as  defined in Section  414(p) of the Code)
         such  separate  Accounts as the  Committee  may deem to be necessary or
         appropriate to reflect such alternate  payee's interest in the Accounts
         of such Participant.  Such alternate payee's Accounts shall be credited
         with the alternate  payee's interest in the  Participant's  Accounts as
         


                                       19





         determined under such qualified domestic relations order. The alternate
         payee  may  change  investment  direction  with  respect  to his or her
         Account  balances in  accordance with Section 4.2 in the same manner as
         the Participant.

               (b)  Except to  the extent  otherwise  provided in  the qualified
         domestic  relations  order naming an alternate  payee with respect to a
         Participant,  (i) the alternate  payee may designate a beneficiary on a
         form  prescribed  by and  filed  with  the  Committee,  (ii) if no such
         beneficiary is validly designated or if the designated beneficiary is a
         person who  predeceases  the alternate  payee,  the  beneficiary of the
         alternate payee shall be the alternate  payee's  estate,  and (iii) the
         beneficiary of the alternate payee shall be accorded under the Plan all
         of the rights and privileges of the beneficiary of a Participant.

               (c)  An alternate payee named with respect to a Participant shall
         be entitled to receive a distribution  from the Plan in accordance with
         the  qualified  domestic  relations order naming such alternate  payee.
         Such distribution may  be made  only in a form provided under the  Plan
         and shall  include only  such amounts  as  are vested.  If a  qualified
         domestic  relations order so provides,  a lump sum  distribution of the
         total vested amount credited to the alternate  payee's  Accounts may be
         made  to the  alternate  payee  at any  time  prior  to  the  date  the
         Participant  named in such qualified  domestic  relations order attains
         his or her earliest retirement age (as defined in Section  414(p)(4)(B)
         of the Code).

               (d)  If  a  portion  of  any  unvested  amount  credited  to  the
         Matching  Account  of a  Participant  named in the  qualified  domestic
         relations  order is credited to the Matching  Account of the  alternate
         payee named in such qualified  domestic  relations  order,  the portion
         credited to such  Account of the  alternate  payee shall vest and/or be
         forfeited  at the same time and in the same  manner as such  Account of
         the Participant.


                                  ARTICLE VII.

                               PLAN ADMINISTRATION

         Section 7.1  Matching  Plan Committee.  The plan administrator  of  the
Plan shall be a Matching Plan Committee  composed of at least three  individuals
appointed by the Board of Directors of the Company. Each member of the Committee
so appointed  shall serve in such office until his or her death,  resignation or
removal by the Board of Directors of the Company.  The Board of Directors of the
Company  may remove any member of the  Committee  at any time by giving  written
notice  thereof to the members of the  Committee.  Vacancies  shall  likewise be
filled from time to time by the Board of Directors  of the Company.  The members
of the Committee shall receive no remuneration  from the Plan for their services
as Committee members.


                                       20





         Section  7.2  Powers, Duties  and  Liabilities  of the  Committee.  The
Committee  shall  have  discretionary  and  final  authority  to  interpret  and
implement the provisions of the Plan,  including without limitation authority to
determine  eligibility for benefits under the Plan, and shall perform all of the
duties and  exercise  all of the powers and  discretion  granted to it under the
terms of the Plan.  The Committee  shall act by a majority of its members at the
time in office and such action may be taken  either by a vote at a meeting or in
writing without a meeting.  The Committee may by such majority action  authorize
any one or more of its members to execute any document or documents on behalf of
the Committee,  in which event the Committee shall notify the Trustee in writing
of such action and the name or names of its member or members so  authorized  to
act.  Every  interpretation,  choice,  determination  or other  exercise  by the
Committee of any discretion given either expressly or by implication to it shall
be  conclusive  and binding upon all parties  directly or  indirectly  affected,
without  restriction,  however,  on the right of the Committee to reconsider and
redetermine such actions.  In performing any duty or exercising any power herein
conferred,  the  Committee  shall in no event perform such duty or exercise such
power  in  any  manner  which  discriminates  in  favor  of  Highly  Compensated
Employees.  The Employers  shall  indemnify and hold harmless each member of the
Committee against any claim, cost, expense (including attorneys' fees), judgment
or liability  (including any sum paid in settlement of a claim with the approval
of the  Employers)  arising out of any act or omission to act as a member of the
Committee appointed under this Plan, except in the case of willful misconduct.

         Section 7.3  Rules, Records and Reports.  The  Committee may adopt such
rules and procedures for the  administration  of the Plan as are consistent with
the terms hereof, and shall keep adequate records of the Committee's proceedings
and acts and of the status of the  Participants'  Accounts.  The  Committee  may
employ  such  agents,   accountants  and  legal  counsel  (who  may  be  agents,
accountants  or legal  counsel for an  Employer) as may be  appropriate  for the
administration  of the Plan. The Committee shall at least annually  provide each
Participant  with a report  reflecting  the status of his or her Accounts in the
Trust and shall  cause  such  other  information,  documents  or  reports  to be
prepared,  provided  and/or  filed  as may  be  necessary  to  comply  with  the
provisions of the Employee  Retirement  Income Security Act of 1974 or any other
law.

         Section 7.4  Administration Expenses and Taxes.  Unless otherwise  paid
by the Employers in their discretion,  the Committee shall direct the Trustee to
pay all  reasonable  and  necessary  expenses  (including  the  fees of  agents,
accountants and legal counsel)  incurred by the Committee in connection with the
administration of the Plan. Should any tax of any character  (including transfer
taxes) be levied upon the Trust assets or the income  therefrom,  such tax shall
be paid from and charged against the assets of the Trust.



                                       21





                                  ARTICLE VIII.

                            AMENDMENT AND TERMINATION

         Section 8.1  Amendment.  The Board of Directors  of  the  Company shall
have the right and power at any time and from time to time to amend  this  Plan,
in whole or in part, on behalf of all Employers.  Any such amendment made by the
Board of Directors  of the Company  shall be made by or pursuant to a resolution
duly adopted by the Board of Directors of the Company, and shall be evidenced by
such resolution or by a written instrument  executed by such person as the Board
of Directors of the Company shall  authorize for such purpose.  With the consent
of the Board of Directors of the Company and subject to such procedure as it may
prescribe,  the Board of  Directors  of each  Employer  shall have the right and
power at any time and from time to time to amend this Plan, in whole or in part,
with respect to the Plan's  application  to the  Participants  of the particular
amending  Employer  and the assets  held in the Trust for their  benefit,  or to
transfer  such assets or any  portion  thereof to a new trust for the benefit of
such Participants.  However, in no event shall any amendment or new trust permit
any portion of the trust fund to be used for or  diverted  to any purpose  other
than the exclusive  benefit of the  Participants  and their  beneficiaries,  nor
shall any amendment or new trust reduce a  Participant's  Vested  Interest under
the Plan.

         Section 8.2  Termination.  The Board of Directors of the Company  shall
have the  right and  power at any time to  terminate  this Plan on behalf of all
Employers,  or to terminate this Plan as it applies to the  Participants who are
or were employees of any particular  Employer,  by giving written notice of such
termination  to the  Committee  and Trustee.  Any  provision of this Plan to the
contrary  notwithstanding,  upon the  termination or partial  termination of the
Plan  as to any  Employer,  or in  the  event  any  Employer  should  completely
discontinue  making  contributions to the Plan without formally  terminating it,
all  amounts  credited  to the  Accounts of the  affected  Participants  of that
particular Employer shall be fully vested.


                                   ARTICLE IX.

                              TOP-HEAVY PROVISIONS

         Section 9.1  Top-Heavy   Definitions.   Unless   the   context  clearly
indicates otherwise, when used in this Article:

               (a)  "Top-Heavy Plan" means this Plan if, as of the Determination
         Date,  the  aggregate of the  Accounts of Key  Employees under the Plan
         exceeds  60% of the  aggregate  of the Accounts of all Participants and
         former  Participants  under the Plan. The aggregate of  the Accounts of
         any Participant or former  Participant  shall include any distributions
         (other than related rollovers or  transfers  from  the Plan  within the
         meaning of  regulations  under  Section  416(g) of the Code)  made from
         


                                       22





         such  individual's  Accounts  during  the Plan  Year or any of the four
         preceding Plan Years, but shall not include any unrelated  rollovers or
         transfers (within the  meaning  of regulations  under Section 416(g) of
         the Code) made to such individual's  Accounts  after December 31, 1983.
         The Accounts of any  Participant or former Participant who (i) is not a
         Key Employee for the  Plan Year in question  but who was a Key Employee
         in a prior Plan Year,   or (ii) has not  completed  an Hour of  Service
         during  the  five-year period ending  on the Determination  Date, shall
         not be taken  into account.  The  determination  of whether the Plan is
         a  Top-Heavy  Plan  shall be made after  aggregating all other plans of
         an Employer and any  Affiliated Company qualifying under Section 401(a)
         of the Code in which a Key Employee is a  participant  or which enables
         such a plan to meet the  requirements  of  Section  401(a)(4) or 410 of
         the Code,  and  after  aggregating any  other plan of  an  Employer  or
         Affiliated   Company,  which   is  not  already   aggregated,  if  such
         aggregation group would  continue to meet the  requirements of Sections
         401(a) (4) and  410  of the  Code  and if such  permissive  aggregation
         thereby  eliminates  the  top-heavy  status  of  any  plan  within such
         permissive aggregation group. The determination of whether this Plan is
         a Top-Heavy Plan shall be made in accordance with Section 416(g) of the
         Code.

               (b)  "Determination  Date" means,  for  purposes  of  determining
         whether the Plan is a Top-Heavy  Plan for a particular  Plan Year,  the
         last day of the preceding Plan Year.

               (c)  "Key  Employee"  means any  Employee  or  former  Employee
         (including a beneficiary  of such  Employee or former  Employee) who at
         any time during the Plan Year or any of the four  preceding  Plan Years
         is:

                    (1)  an officer of the Employer who has Compensation for any
               such  Plan  Year  greater  than 50% of the amount in effect under
               Section  415(b)(1)(A)  of the Code for such Plan
               Year;

                    (2)  one  of the  10  Employees   owning  (or  considered as
               owning  within  the  meaning  of  Section  318 of  the Code)  the
               largest   interests   in   excess  of  0.5%  in  an  Employer  or
               Affiliated  Company and having  Compensation for such  Plan  Year
               of more than the limitation in effect under Section  415(c)(1)(A)
               of the Code;

                    (3)  a person  owning (or  considered as  owning  within the
               meaning  of  Section  318  of the  Code)  more  than  5%  of  the
               outstanding stock of an Employer or stock possessing more than 5%
               of the total  combined voting power of all stock  of an Employer;
               or



                                       23





                    (4)  a person  who has  Compensation for such Plan Year from
               an Employer of more than $150,000  and who would be  described in
               paragraph (3) hereof if 1% were  substituted for 5% in each place
               it appears in such paragraph.

         For the purposes of applying Section 318 of the Code to this subsection
         (c), subparagraph (C) of Section 318(a)(2) of the Code shall be applied
         by substituting  5% for 50%. The rules of subsections  (b), (c) and (m)
         of Section 414 of the Code shall not apply for purposes of  determining
         ownership in an Employer under this subsection (c).

               (d)  "Non-Key  Employee"  means  any  Employee or former Employee
         (including a beneficiary  of such  Employee or former  Employee) who is
         not a Key Employee.

         Section 9.2  Minimum  Contribution Requirement.  Any  provision of this
Plan to the contrary  notwithstanding,  if the Plan is a Top-Heavy  Plan for any
Plan Year commencing after December 31, 1996, then the Employers will contribute
to the  Matching  Account  of each  Non-Key  Employee  who is both  eligible  to
participate  and in the employ of an Employer on the last day of such Plan Year,
an amount which, when added to the total amount of contributions and forfeitures
otherwise  allocable  under the Plan for such  Non-Key  Employee  for such year,
shall  equal  the  lesser  of  (i)  3% of  such  Non-Key  Employee's  Limitation
Compensation (Compensation for any Plan Year commencing after December 31, 1997)
for such year or (ii) the amount of contributions and forfeitures  (expressed as
a  percentage  of  Limitation  Compensation  (Compensation  for  any  Plan  Year
commencing  after  December  31,  1997))  allocable  under  the Plan for the Key
Employee for whom such  percentage is the highest for the Plan Year after taking
into account  contributions under other defined contribution plans maintained by
the Employer in which a Key Employee is a participant (as well as any other plan
of an Employer  which  enables such a plan to meet the  requirements  of Section
401(a)(4) or 410 of the Code);  provided,  however, that no minimum contribution
shall be made for a Non-Key Employee under this Section for any Plan Year if the
Employer  maintains  another  qualified  plan under  which a minimum  benefit or
contribution  is  being  accrued  or made  for such  Plan  Year for the  Non-Key
Employee in accordance  with Section 416(c) of the Code. A Non-Key  Employee who
is not a  Participant,  but for whom a  contribution  is made  pursuant  to this
Section,  shall be accorded all of the rights and  privileges  of a  Participant
under the Plan except that no contributions  (other than contributions  pursuant
to this Section)  shall be made for or on behalf of such Non-Key  Employee until
he or she meets the eligibility and participation requirements of Article II.


                                   ARTICLE X.

                        MISCELLANEOUS GENERAL PROVISIONS

         Section 10.1  Spendthrift Provision.   No  right  or  interest  of  any
Participant  or  beneficiary  under  the Plan may be  assigned,  transferred  or


                                       24





alienated,  in whole or in part,  either directly or by operation of law, and no
such right or interest shall be liable for or subject to any debt, obligation or
liability of such Participant or beneficiary;  provided,  however,  that nothing
herein shall prevent the payment of amounts from a Participant's  Accounts under
the Plan in  accordance  with the terms of a court order which the Committee has
determined  to be a qualified  domestic  relations  order (as defined in Section
414(p) of the Code).

         Section 10.2  Claims Procedure.  If any person  (hereinafter called the
"Claimant") feels that he or she is being denied a benefit to which he or she is
entitled under the Plan, such Claimant may file a written claim for said benefit
with any member of the  Committee.  Within 60 days of the  receipt of such claim
the Committee shall determine and notify the Claimant as to whether he or she is
entitled to such benefit.  Such notification shall be in writing and, if denying
the claim for benefit,  shall set forth the  specific  reason or reasons for the
denial,  make specific  reference to the pertinent  provisions of the Plan,  and
advise the  Claimant  that he or she may,  within 60 days of the receipt of such
notice,  in writing  request to appear  before  the  Committee  for a hearing to
review  such  denial.  Any  such  hearing  shall  be  scheduled  at  the  mutual
convenience of the Committee or its designated  representative and the Claimant,
and  at  such   hearing  the  Claimant   and/or  his  or  her  duly   authorized
representative  may examine any  relevant  documents  and present  evidence  and
arguments  to support  the  granting  of the benefit  being  claimed.  The final
decision of the Committee with respect to the claim being reviewed shall be made
within 60 days following the hearing  thereon and the Committee shall in writing
notify the Claimant of its final decision, again specifying the reasons therefor
and the pertinent  provisions of the Plan upon which such decision is based. The
final decision of the Committee shall be conclusive and binding upon all parties
having or claiming to have an interest in the matter being reviewed.

         Section 10.3 Maximum  Contribution  Limitation.  Any  provision of this
Plan to the contrary notwithstanding, the sum of (i) the Employer contributions,
(ii)  the  forfeitures,  and  (iii)  the  Participant  contributions  (excluding
rollover  contributions  and employee  contributions  to a  simplified  employee
pension  allowable as a deduction,  each within the meaning specified in Section
415(c)(2) of the Code),  allocated to a Participant  with respect to a Plan Year
shall in no event exceed the lesser of $30,000 (as adjusted  pursuant to Section
415(d) of the Code to take into account any  cost-of-living  increase) or 25% of
such  Participant's  Limitation  Compensation  (Compensation  for any Plan  Year
commencing  after December 31, 1997) for that year. For the purposes of applying
the  limitation  imposed  by this  Section,  each  Employer  and its  Affiliated
Companies shall be considered a single  employer,  and all defined  contribution
plans  (meaning plans  providing for individual  accounts and for benefits based
solely  upon the  amounts  contributed  to such  accounts  and any  forfeitures,
income,  expenses,  gains and losses  allocated to such  accounts)  described in
Section 415(k) of the Code, whether or not terminated, maintained by an Employer
or its  Affiliated  Companies  shall be  considered a single plan.  If the total
amount allocable to a Participant's  Matching Account for a particular Plan Year
would,  but for this  sentence,  exceed the  foregoing  limitation,  any amounts
allocated  to such  Participant's  Matching  Account in excess of the  foregoing



                                       25




limitation shall be credited to a suspense account and thereafter used to reduce
Matching  Contributions  for  such  Plan  Year  (and,  if  necessary,  the  next
succeeding year).

         Section 10.4  Employment Noncontractual. The establishment of this Plan
shall not enlarge or  otherwise  affect the terms of any  Employee's  employment
with an Employer and an Employer may terminate the employment of any Employee as
freely and with the same effect as if this Plan had not been adopted.

         Section  10.5  Limitations  on  Responsibility.  The  Employers  do not
guarantee or indemnify the Trust against any loss or  depreciation of its assets
which may occur,  nor  guarantee  the  payment  of any  amount  which may become
payable to a Participant or his or her beneficiaries  pursuant to the provisions
of this Plan. All payments to Participants and their beneficiaries shall be made
by the Trustee at the direction of the  Committee  solely from the assets of the
Trust  and the  Employers  shall  have no legal  obligation,  responsibility  or
liability for any such payments.

         Section  10.6  Merger or  Consolidation.   In no event shall this  Plan
be merged or  consolidated  into or with any  other  plan,  nor shall any of its
assets or liabilities be transferred to any other plan,  unless each Participant
would be  entitled  to  receive  a  benefit  if the plan in which he or she then
participates  terminated  immediately  following such merger,  consolidation  or
transfer,  which is equal to or  greater  than the  benefit he or she would have
been entitled to receive if the Plan had been  terminated  immediately  prior to
such merger, consolidation or transfer.

         Section 10.7  Applicable Law. This Plan shall be governed and construed
in  accordance  with the  internal  laws  (and not the  principles  relating  to
conflicts of laws) of the State of Texas except where superseded by federal law.

         IN WITNESS  WHEREOF,  this Plan has been  restated  by Pioneer  Natural
Resources  USA,  Inc.  this 11th day of  November,  1997,  to be effective as of
October 1, 1997.

                                          PIONEER NATURAL RESOURCES USA, INC.




                                          By    /s/ Larry Paulsen
                                            ------------------------------------
                                            Title: Vice President


                                      26