Exhibit 5.1


                         [LETTERHEAD OF McKESSON HBOC]

                               February 5, 1999



McKesson HBOC, Inc.
McKesson Plaza
One Post Street
San Francisco, California 94104


  Re:    McKesson HBOC, Inc.  -- Registration Statement on Form S-8
         -----------------------------------------------------------

Ladies and Gentlemen:

I am Senior Vice President and General Counsel of McKesson HBOC, Inc., a
Delaware corporation (the "Company"), and am issuing this opinion in connection
with the Registration Statement on Form S-8 being filed by the Company with the
Securities and Exchange Commission (the "Commission") on the date hereof (the
"Registration Statement") for the purpose of registering with the Commission
under the Securities Act of 1933, as amended (the "Securities Act"), 700,000
shares (the "Shares") of common stock of the Company, par value $0.01 per share,
to be issued by the Company pursuant to the McKesson HBOC, Inc. 1999 Executive
Stock Purchase Plan (the "Plan").

In this connection, I have reviewed the Registration Statement, as proposed to
be filed with the Commission.  As General Counsel, I am familiar with the
Restated Certificate of Incorporation of the Company, as amended, and the
Restated By-laws of the Company, as amended, each as currently in effect. I
have also examined originals or copies, certified or otherwise identified to
my satisfaction of such records of the Company and such instruments,
certificates of public officials, and such other documents, certificates and
records as I have deemed necessary or appropriate as a basis for the opinion
set forth herein.

In my examination, I have assumed the genuineness of all signatures, the legal
capacity of natural persons, the authenticity of all documents submitted to me
as originals, the conformity to original documents of all documents submitted to
me as certified, conformed or photostatic copies and the authenticity of the
originals of such copies.  In making my examination of documents executed or to
be executed by parties other than the Company, I have assumed that such parties
had or will have the power, corporate or other, to enter into and perform all
obligations thereunder and have also assumed the due authorization by all
requisite action, corporate or other, and execution and delivery by such parties
and the validity and binding effect thereof.  As to any facts material to the
opinion expressed herein which I have not independently established or verified,
I have relied upon statements and representations of other officers and
representatives of the Company and others.

 
I am admitted to the Bar of the State of California and do not purport to be an
expert on, or express any opinion concerning, any law other than the substantive
law of the State of California.

Based upon and subject to the foregoing, I am of the opinion that the Shares,
when issued and sold in accordance with the terms of the Plan, will be legally
issued, fully paid and nonassessable.

I hereby consent to the filing of this opinion as an exhibit to the Registration
Statement.

This opinion is furnished by me, as counsel to the Company, in accordance with
the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act
and, except as provided in the immediately preceding paragraph, is not to be
used, circulated or quoted for any other purpose or otherwise referred to or
relied upon by any other person without the express written permission of the
Company.

                                        Very truly yours,

                                        /s/ Ivan D. Meyerson
                                        -------------------------------
                                        Ivan D. Meyerson