FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * HAMMERGREN JOHN H   2. Issuer Name and Ticker or Trading Symbol MCKESSON CORP [MCK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chairman, President & CEO (Last) (First) (Middle) ONE POST STREET 3. Date of Earliest Transaction (Month/Day/Year) 05/22/2011 (Street) SAN FRANCISCO, CA 94104 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 05/22/2011   M   96,525 A $ 0 635,314.925 (1) I By Trust Common Stock 05/22/2011   F   45,058 (2) D $ 85.07 590,256.925 (6) I By Trust Common Stock               4,023.2991 I By Profit-Sharing Investment Plan

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Restricted Stock Units

$ 0

05/22/2011

M

96,525

(5)

(5)

Common Stock

96,525

$ 0

0

D

Restricted Stock Units

$ 0

05/24/2011

A

220,980

(3)

(3)

Common Stock

220,980

$ 0

220,980

D

Employee Stock Options (Right-to-buy)

$ 83.51

05/24/2011

A

301,000

(4)

05/24/2018

Common Stock

301,000

$ 0

301,000

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
HAMMERGREN JOHN H ONE POST STREET SAN FRANCISCO, CA 94104	X		Chairman, President & CEO

Signatures

Donna Spinola, Attorney-in-fact		05/24/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Represents 474,390.925 shares held under the Hammergren Family Trust; 13,664 under the JHH 2009 GRAT #5; 13,664 under the WLH 2009 GRAT #5; 13,664 under the JHH 2009 GRAT #6; 13,664 under the WLH 2009 GRAT #6; 13,664 under the JHH 2009 GRAT #7; 13,664 under the WLH 2009 GRAT#7; 13,665 under the JHH 2009 GRAT #8; 13,665 under the WLH 2009 GRAT #8; 12,900 under the JHH 2010 GRAT #3; 12,900 under the WLH 2010 GRAT #3; 12,905 under the JHH 2010 GRAT #4; 12,905 under the WLH 2010 GRAT #4.
(2)	This transaction represents a withholding of shares to cover taxes applicable to a vesting of RSUs also reported on this Form 4.
(3)	These units vest 100% on 05/24/2014.
(4)	This option granted 05/24/2011 vests 25% per year commencing on the first anniversary of the grant date.
(5)	These units vested 50% 5/22/2009 and 50% 5/22/2011.
(6)	Represents 429,332.925 shares held under the Hammergren Family Trust; 13,664 under the JHH 2009 GRAT #5; 13,664 under the WLH 2009 GRAT #5; 13,664 under the JHH 2009 GRAT #6; 13,664 under the WLH 2009 GRAT #6; 13,664 under the JHH 2009 GRAT #7; 13,664 under the WLH 2009 GRAT#7; 13,665 under the JHH 2009 GRAT #8; 13,665 under the WLH 2009 GRAT #8; 12,900 under the JHH 2010 GRAT #3; 12,900 under the WLH 2010 GRAT #3; 12,905 under the JHH 2010 GRAT #4; 12,905 under the WLH 2010 GRAT #4.

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