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-Q for the quarterly  period ended  September 30,
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:   October 31, 2003