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 Canada Inc.......................................... Canada Medis Health and Pharmaceutical Services Inc............... Canada GM Holdings, Inc............................................. Delaware McKesson General Medical Corp.............................. Virginia