EXHIBIT 99.1

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                    AS ADOPTED PURSUANT TO SECTION 906 OF THE
                           SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of the National-Oilwell Retirement and
Thrift Plan (the "Plan") on Form 11-K for the year ended December 31, 2002, as
filed with the Securities and Exchange Commission on June 24, 2003 (the
"Report"), I, Daniel L. Molinaro, Member of the National-Oilwell Benefits Plan
Administrative Committee, certify, pursuant to 18 U.S.C. Section 1350, as
adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 ("Section
906"), that:

         (1)    The Report fully complies with the requirements of Section 13(a)
                of the Securities Exchange Act of 1934; and

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

    June 24, 2003             /s/ Daniel L. Molinaro
---------------------         -------------------------------------------------
        Date                  Daniel L. Molinaro
                              Member of the National-Oilwell Benefits Plan
                              Administrative Committee

A signed original of this written statement required by Section 906 has been
provided to the Plan and will be retained by the Plan and furnished to the
Securities and Exchange Commission or its staff upon request.