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EXHIBIT 24.2


                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS THAT the undersigned directors and
officers of McKesson Corporation, a Delaware corporation (the "Company") do
hereby constitute and appoint Ivan D. Meyerson and Kristina Veaco his or her
true and lawful attorney and agent, each with full power and authority (acting
alone and without the other) to execute in the name and on behalf of the
undersigned as such Director and/or Officer, a Registration Statement on Form
S-8 under the Securities Act of 1933, as amended, with respect to the
registration of shares of the Company's Common Stock, par value $.01 per share,
that may be issued by the Company under the McKesson Corporation 1997
Non-Employee Directors' Equity Compensation and Deferral Plan, and to execute
any and all amendments to such Registration Statement, whether filed prior or
subsequent to the time such Registration Statement becomes effective. The
undersigned hereby grants unto such attorneys and agents, and each of them, full
power of substitution and revocation in the premises and hereby ratifies and
confirms all that such attorneys and agents may do or cause to be done by virtue
of these presents.




/s/ NIGEL REES
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Nigel Rees
Vice President and Controller


Dated:  August 13, 2001