Exhibit 5.1

                   [VARIAN MEDICAL SYSTEMS, INC. LETTERHEAD]

                                March 14, 2001


Varian Medical Systems, Inc.
3050 Hansen Way
Palo Alto, California 94304

Re:  Varian Medical Systems Inc., Deferred Compensation Plan
     -------------------------------------------------------

Ladies and Gentlemen:

     With reference to the Registration Statement on Form S-8 to be filed by
Varian Medical Systems, Inc., a Delaware corporation (the "Company"), with the
Securities and Exchange Commission under the Securities Act of 1933, relating to
deferred compensation obligations ("Deferred Compensation Obligations") of the
Company, to be offered and sold under the Company's Deferred Compensation Plan
(the "Plan"), it is my opinion that (1) the Deferred Compensation Obligations
when established pursuant to the terms of the Plan will be valid and binding
obligations of the Company, enforceable against the Company in accordance with
their terms and the terms of the Plan, except as enforceability (i) may be
limited by bankruptcy, insolvency, reorganization or other similar laws
effecting creditors' rights generally, and (ii) subject to general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law) and (2) any shares of the Common Stock of the Company,
delivered in accordance with the Plan, will be legally issued, fully paid and
nonassessable.

     I hereby consent to the filing of this opinion with the Securities and
Exchange Commission as Exhibit 5.1 to the Registration Statement.


                                   Very truly yours,



                                   /s/ Joseph B. Phair

                                   Joseph B. Phair, Esq.