Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

     We consent to the incorporation by reference in Registration Statement Nos. 333-50261 and 333-84806 of McKesson Corporation on Form S-8 of our report dated September 23, 2005, appearing in this Annual Report on Form 11-K of the McKesson Corporation Profit-Sharing Investment Plan for the fiscal year ended March 31, 2005.

/s/ Deloitte & Touche LLP  

San Francisco, California 

September 23, 2005