EXHIBIT 99.1



                    Certification of Chief Executive Officer
            Pursuant to Section 906 of the Sarbanes-Oxley Act Of 2002
                            (18 U.S.C. Section 1350)



    In connection with the accompanying Annual Report of Tri-Union Development
Corporation (the "Company") on Form 10-K for the year ended December 31, 2002
(the "Report"), I, James M. Trimble, Chairman, President and Chief Executive
Officer of the Company, hereby certify that to my knowledge:

     (1)  The Report fully complies with the requirements of Section 13(a) or
          15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or
          78o(d)); and

     (2)  The information contained in the Report fairly presents, in all
          material respects, the financial condition and results of operations
          of the Company.



Dated:         March 31, 2003                       /s/ James M. Trimble
         ---------------------------           ---------------------------------
                                               James M. Trimble,
                                               Chairman, President and
                                               Chief Executive Officer