EXHIBIT 32.1



                                CERTIFICATION OF
                             CHIEF EXECUTIVE OFFICER
                      OF PIONEER NATURAL RESOURCES COMPANY
                         PURSUANT TO 18 U.S.C. ss. 1350


     I, Scott D. Sheffield,  Chairman,  President and Chief Executive Officer of
Pioneer  Natural  Resources  Company (the  "Company"),  hereby  certify that the
accompanying  report on Form 10-K for the year ended December 31, 2003 and filed
with the  Securities  and  Exchange  Commission  on the date hereof  pursuant to
Section  15(d) of the  Securities  Exchange  Act of 1934 (the  "Report")  by the
Company fully complies with the requirements of that section.

     I further  certify  that the  information  contained  in the Report  fairly
presents,  in all  material  aspects,  the  financial  condition  and results of
operations of the Company.



                                  /s/ Scott D. Sheffield
                                 -------------------------------------------
                         Name:   Scott D. Sheffield, Chairman, President
                                   and Chief Executive Officer
                         Date:   February 2, 2004