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 --------------- HBO & Company................................................ Delaware McKesson Water Products Company.............................. California Medis Health and Pharmaceutical Services Inc. ............... Canada GM Holdings, Inc. ........................................... Delaware McKesson General Medical Corp. .............................. Virginia 25