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                                                                     Exhibit 5.1
 

                                  July 31, 1998


Anergen, Inc.
301 Penobscot Drive
Redwood City, California  94063

       RE:    REGISTRATION STATEMENT ON FORM S-8

Gentlemen:

     We have examined the Registration Statement on Form S-8 to be filed by
Anergen, Inc., a Delaware Corporation (the "Company"), with the Securities and
Exchange Commission on or about July 30, 1998 (the "Registration Statement") in
connection with the assumption pursuant to Rule 414 of the Securities Act of
1933, as amended, by the Company of certain Registration Statements on Form S-8
filed by the Company's predecessor, Anergen, Inc., a California Corporation
("Anergen California"), relating to shares of Common Stock of Anergen California
reserved for issuance under the certain stock plans (the "Plans") of Anergen
California. We understand that the Plans have been assumed by the Company and
that in accordance the terms of the Plans, the Company has reserved shares (the
"Shares") of Common Stock of the Company for issuance pursuant to the Plans. As
your counsel, we have examined the proceedings taken and are familiar with the
proceedings proposed to be taken by you in connection with said issuance and
sale of the Shares pursuant to the Plans.

     It is our opinion that, upon completion of the proceedings being taken or
contemplated by us to be taken prior to the issuance and sale of the Shares
pursuant to the Plans, and upon completion of the proceedings being taken in
order to permit such transaction to be carried out in accordance with the
securities laws of the various states where required, the Shares, when issued
and sold in the manner referred to in the Plans and the Registration Statement,
will be legally and validly issued, fully-paid and non-assessable.

     We consent to the use of this opinion as an exhibit to the Registration
Statement, and further consent to the use of our name wherever appearing in the
Registration Statement, including the prospectus constituting a part thereof,
and any amendments thereto.

                                          Very truly yours,

                                          WILSON SONSINI GOODRICH & ROSATI
                                          Professional Corporation

                                          /s/ Wilson Sonsini Goodrich & Rosati
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