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                                                                    EXHIBIT 8.02

                              FORM OF TAX OPINION

                      [MORRISON & FOERSTER LLP LETTERHEAD]



                                  ____ __, 1999



Ribi Immunochem Research, Inc.
553 Old Corvallis Road
Hamilton, Montana 59840


Ladies and Gentlemen:

        We have acted as counsel for Ribi Immunochem Research, Inc., a Delaware
corporation ("Ribi"), in connection with the preparation and execution of the
Agreement and Plan of Merger dated as of June 9, 1999, by and Ribi and Corixa
Corporation, a Delaware corporation ("Corixa"). Pursuant to the Agreement, Ribi
will merge with and into Corixa (the "Merger"). Unless otherwise defined,
capitalized terms referred to herein have the meanings set forth in the
Agreement. All section references, unless otherwise indicated, are to the
Internal Revenue Code of 1986, as amended (the "Code").

        You have requested our opinion regarding certain United States federal
income tax consequences of the Merger. In delivering this opinion, we have
reviewed and relied upon (without any independent investigation) the facts,
statements, descriptions and representations set forth in the Agreement
(including Exhibits), the registration statement on Form S-4 filed with the
Securities and Exchange Commission (which includes a proxy statement-prospectus
relating to the Merger) (the "Registration Statement"), and such other documents
pertaining to the Merger as we have deemed necessary or appropriate. We have
also relied upon (without any independent investigation) certificates of
officers of Corixa and Ribi, respectively (the "Officers' Certificates") in
forms attached hereto as Exhibits A and B.

        In connection with rendering this opinion, we have also assumed (without
any independent investigation) that:

        1. At all relevant times prior to and including the Effective Date, (i)
no outstanding indebtedness of Ribi or Corixa has or will represent equity for
tax purposes; (ii) no outstanding equity of Ribi or Corixa has represented or
will represent indebtedness for tax purposes; (iii) no outstanding security,
instrument, agreement or arrangement that provides for, contains, or represents
either a right to acquire Ribi's

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                            MORRISON & FOERSTER LLP

Corixa Corporation
____ __, 1999
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capital stock (or to share in the appreciation thereof) constitutes or will
constitute "stock" for purposes of Section 368(c) of the Code.

        2. Original documents (including signatures) are authentic, documents
submitted to us as copies conform to the original documents, and there has been
(or will be by the Effective Time) due execution and delivery of all documents
where due execution and delivery are prerequisites to effectiveness thereof.

        3. Any representation or statement referred to above made "to the
knowledge of," "to the best of the knowledge" or otherwise similarly qualified
is correct without such qualification. As to all matters in which a person or
entity making a representation referred to above has represented that such
person or entity either is not a party to, does not have, or is not aware of,
any plan, intention, understanding or agreement, there is in fact no such plan,
intention, understanding or agreement.

        4. All statements, descriptions and representations contained in any of
the documents referred to herein or otherwise made to us are true and correct in
all material respects and will continue to be true and correct in all material
respects as of the Effective Time and all other relevant times, and no actions
have been (or will be) taken which are inconsistent with such representations.

        5. The Merger will be reported by Corixa and Ribi on their respective
federal income tax returns in a manner consistent with the opinion set forth
below.

        6. The Merger will be consummated in accordance with the Agreement (and
without any waiver, breach or amendment of any of the provisions thereof) and
will be effective under the applicable state laws.

        7. An opinion of counsel, substantially identical in substance to this
opinion, has been delivered to Ribi from Morrison & Foerster LLP, and will not
be withdrawn prior to the Effective Date.

        Based on our examination of the foregoing items and subject to the
assumptions, exceptions, limitations and qualifications set forth herein and in
the Registration Statement, we are of the opinion that if the Merger is
consummated in accordance with the provisions of the Agreement (and without any
waiver, breach or amendment of any of the provisions thereof) and the statements
set forth in the Officers' Certificates are true and correct as of the Effective
Time:

               (a) the Merger will be a "reorganization" for federal income tax
purposes within the meaning of Section 368(a) of the Code;

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                            MORRISON & FOERSTER LLP

Corixa Corporation
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               (b) each of Ribi and Corixa will be a "party to a reorganization"
within the meaning of Section 368(b) of the Code; and

               (c) the disclosure of the material federal income tax
consequences of the Merger to Ribi stockholders in the Registration Statement
under the heading "Material Federal Income Tax Considerations" is correct in all
material respects, subject to the limitations set forth therein.

        This opinion represents and is based upon our best judgment regarding
the application of federal income tax laws arising under the Code, existing
judicial decisions, administrative regulations and published rulings and
procedures. Our opinion is not binding upon the Internal Revenue Service or the
courts, and there is no assurance that the Internal Revenue Service will not
successfully assert a contrary position. Furthermore, no assurance can be given
that future legislative, judicial or administrative changes, on either a
prospective or retroactive basis, would not adversely affect the accuracy of the
conclusions stated herein. Nevertheless, we undertake no responsibility to
advise you of any new developments in the application or interpretation of the
federal income tax laws.

        This opinion concerning certain of the U.S. federal tax consequences of
the Merger is limited to the specific U.S. federal tax consequences presented
above, and does not address any other federal, state, local or foreign tax
consequences that may result from the Merger or any other transaction (including
any transaction undertaken in connection with the Merger).

        No opinion is expressed as to any transaction other than the Merger as
described in the Agreement or to any transaction whatsoever, including the
Merger, if all the transactions described in the Agreement are not consummated
in accordance with the terms of such Agreement and without waiver or breach of
any material provision thereof or if all of the representations, warranties,
statements and assumptions upon which we relied are not true and accurate at all
relevant times. In the event any one of the statements, representations,
warranties or assumptions upon which we have relied to issue this opinion is
incorrect, our opinion might be adversely affected and may not be relied upon.

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                            MORRISON & FOERSTER LLP

Corixa Corporation
____ __, 1999
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        We consent to the use of this opinion as an exhibit to the Registration
Statement, to references to this opinion in the Registration Statement and to
the use of our name in the Registration Statement under the heading "Material
Federal Income Tax Consequences" therein. In giving this consent, we do not
admit that we are within the category of persons whose consent is required under
Section 7 of the Securities Act of 1933, as amended, or the rules or regulations
promulgated thereunder. The filing of this opinion as an exhibit to the S-4
Registration Statement and the references to the opinion and our firm therein
are not intended to create liability under applicable state law to any person
other than Corixa, our client.

                                             Very truly yours,


                                             MORRISON & FOERSTER LLP