1

                                                                    EXHIBIT 5.01


                                October 29, 1998



AG Associates, Inc.
4425 Fortran Drive
San Jose, CA 95134

Gentlemen/Ladies:

     At your request, we have examined the Registration Statement on Form S-8
(the "Registration Statement"), to be filed by you with the Securities and
Exchange Commission (the "SEC") on or about October 30, 1998, in connection with
the registration under the Securities Act of 1933, as amended, of an aggregate
of 400,000 shares of your Common Stock (the "Stock") subject to issuance by you
upon the exercise of stock options granted or to be granted by you under your
1993 Stock Option Plan (the " Plan").

     In rendering this opinion, we have examined the following:


     (1)  your Registration Statement on Form S-1 (Registration Number
          33-90382), as declared effective by the SEC on May 15, 1995, together
          with the Exhibits filed as a part thereof;

     (2)  the Registration Statement, together with the Exhibits filed as a part
          thereof, including, without limitation, the Plan and related stock
          option grant and exercise agreements;

     (3)  the Prospectus prepared in connection with the Registration Statement;

     (4)  the minutes of meetings and actions by written consent of your
          shareholders and your Board of Directors that are contained in your
          minute books that are in our possession;

     (5)  your stock records in our possession that you have provided to us
          (consisting of a list of shareholders and a list of option holders
          respecting your capital stock that were prepared by you and dated
          October 28, 1998);

     (6)  your Registration Statement on Form 8-A (Commission File Number
          000-25862), as declared effective by the SEC on May 15, 1995;

     (7)  your Registration Statement on Form S-8 (Registration Number
          33-94716), as declared effective by the SEC on July 19, 1995;

     (8)  your Registration Statement on Form S-8 (Registration Number
          333-02360), as declared effective by the SEC on March 14, 1996; and

     (9)  a Management Certificate of even date herewith, duly executed and
          delivered by you.

   2

     In our examination of documents for purposes of this opinion, we have
assumed, and express no opinion as to, the genuineness of all signatures on
original documents, the authenticity of all documents submitted to us as
originals, the conformity to originals of all documents submitted to us as
copies, the lack of any undisclosed terminations, modifications, waivers or
amendments to any documents reviewed by us and the due execution and delivery of
all documents where due execution and delivery are prerequisites to the
effectiveness thereof.

     As to matters of fact relevant to this opinion, we have relied solely upon
our examination of the documents referred to above and have assumed the current
accuracy and completeness of the information obtained from public officials and
records included in the documents referred to above. We have made no independent
investigations or other attempts to verify the accuracy of any of such
information or to determine the existence or non-existence of any other factual
matters; however, we are not aware of any facts that would lead us to believe
that the opinion expressed herein is not accurate.

     Based on the foregoing, it is our opinion that the 400,000 shares of Stock
that may be issued and sold by you upon the exercise of stock options granted or
to be granted under the Plan when issued and sold in the manner referred to in
the Plan, and the prospectus associated with such Plan, will be validly issued,
fully paid and nonassessable.

     We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to all references to us, if any, in the
Registration Statement, the Prospectus constituting a part thereof and any
amendments thereto.

     This opinion speaks only as of its date and is intended solely for the your
use as an exhibit to the Registration Statement for the purpose of the above
sale of the Stock and is not to be relied upon for any other purpose.

                                             Very truly yours,

                                             FENWICK & WEST LLP



                                             By:  /s/ Gail E. Suniga
                                                ------------------------