10-K                                                                  EXHIBIT 24



                                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, under the Securities Act of 1934,
as amended, an annual report on Form 10-K, and thereafter to execute and file
any and all amendments to such Form, whether filed prior or subsequent to the
time such Form 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/ Alfred C. Eckert III                           /s/ Gerald E. Mayo
- ----------------------------------------           -----------------------------
Alfred C. Eckert III, Director                     Gerald E. Mayo, Director


/s/ Tully M. Friedman                              /s/ James V. Napier
- ----------------------------------------           -----------------------------
Tully M. Friedman, Director                        James V. Napier, Director


/s/ William R. Graber                              /s/ Carl E. Reichardt
- ----------------------------------------           -----------------------------
William R. Graber, Senior Vice President           Carl E. Reichardt, Director
and Chief Financial Officer


/s/ John H. Hammergren                             /s/ Alan Seelenfreund
- ----------------------------------------           -----------------------------
John H. Hammergren, President and                  Alan Seelenfreund
Chief Executive Officer and Director               Chairman of the Board


/s/ Alton F. Irby                                  /s/ Jane E. Shaw
- ----------------------------------------           -----------------------------
Alton F. Irby III, Director                        Jane E. Shaw, Director


/s/ M. Christine Jacobs                            /s/ R.F. Syron
- ----------------------------------------           -----------------------------
M. Christine Jacobs, Director                      Richard F. Syron, Director


/s/ Marie L. Knowles                               /s/ Nigel A. Rees
- ----------------------------------------           -----------------------------
Marie L. Knowles, Director                         Nigel A. Rees
                                                   Vice President and Controller

/s/ Martin M. Koffel
Martin M. Koffel, Director


Dated:  May 29, 2002