EXHIBIT 5 March 22, 2002 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 20,000,000 shares of the Company's Common Stock, par value $0.01 per share, issuable pursuant to the McKesson Corporation Profit-Sharing Investment Plan (the "Plan"). As General Counsel, I am familiar with the Company's Restated Certificate of Incorporation and its 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 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 on Form S-8. Very truly yours, /s/Ivan D. Meyerson Ivan D. Meyerson Senior Vice President, General Counsel and Secretary