EXHIBIT 21 SUBSIDIARIES OF THE REGISTRANT There is no parent of the Company. The following is a listing of the significant subsidiaries of the Company, or if indented, subsidiaries of the Company under which they are listed: JURISDICTION OF ORGANIZATION -------------- McKesson Water Products Company......................... California Medis Health and Pharmaceutical Services Inc. .......... Canada General Medical Inc. ................................... Delaware GM Holdings, Inc. .................................... Delaware McKesson General Medical Corp. ..................... Virginia 26