McKESSON CORPORATION


                                                                    EXHIBIT 99.2


                           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 quarterly report of McKesson Corporation (the "Company")
on Form 10-Q for the period ended June 30, 2002 as filed with the Securities and
Exchange Commission on the date hereof (the "Report"), I, William R. Graber,
Chief Financial Officer of the Company certify, pursuant to 18 U.S.C. Section
1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that
to the best of my knowledge:

(1)     The Report fully complies with the requirements of section 13(a) or
        15(d) of the Securities 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
        Company


/s/ William R. Graber
- -------------------------------
WILLIAM R. GRABER
Chief Financial Officer
August 9, 2002

This certification accompanies the Report pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, and shall not, except to the extent required by the
Sarbanes-Oxley Act of 2002, be deemed filed by the Company for the purposes of
Section 18 of the Securities Exchange Act of 1934, as amended.