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                                                                       EXHIBIT 5


                               August 13th, 2001



McKesson Corporation
McKesson Plaza
One Post Street
San Francisco, CA 94104



         I am Senior Vice President, General Counsel and Secretary of McKesson
Corporation, a Delaware corporation (the "Company"). In that capacity I have
reviewed the Registration Statement on Form S-8 to be filed by the Company with
the Securities and Exchange Commission under the Securities Act of 1933 with
respect to 786,000 shares of the Company's Common stock, and options to purchase
shares of the Company's Common stock, par value $0.01 per share, issuable
pursuant to the McKesson Corporation 1997 Non-Employee Directors' Equity
Compensation and Deferral Plan (the "Directors' Plan"). As General Counsel, I am
familiar with the Company's Restated Certificate of Incorporation and its
Amended and Restated By-Laws, as amended to date. I have also examined such
other documents, corporate records and instruments as I have deemed necessary or
appropriate for the purpose of this opinion.

         Based upon the foregoing, I am of the opinion that the shares of Common
Stock of the Company, when issued in accordance with the Directors' Plan, will
be legally issued, fully paid and nonassessable.

         I hereby consent to the filing of this opinion with the Securities and
Exchange Commission as Exhibit 5 to the Registration Statement.

                                        Very truly yours,


                                        /s/ IVAN D. MEYERSON
                                        ----------------------------------------
                                        Ivan D. Meyerson
                                        Senior Vice President,
                                        General Counsel and Corporate Secretary