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                                                                     EXHIBIT 8.2


                                                                October 12, 2001



Dime Bancorp, Inc.,
      589 Fifth Avenue,
           New York, New York 10017.

Ladies and Gentlemen:

        We have acted as counsel to Dime Bancorp, Inc., a Delaware corporation
(the "Company"), in connection with the planned merger of the Company with and
into Washington Mutual, Inc., a Washington corporation ("Washington Mutual"),
pursuant to the Agreement and Plan of Merger, dated as of June 25, 2001 by and
between Washington Mutual and the Company (the "Merger Agreement") as described
in the Joint Proxy Statement/Prospectus (the "Joint Proxy Statement/Prospectus")
of Washington Mutual and the Company, dated October 12, 2001, which is part of
the registration statement on Form S-4 of Washington Mutual, to which this
opinion is attached as an exhibit. Capitalized terms used and not defined herein
shall have the meaning set forth in the Merger Agreement.

        For purposes of this opinion, we have reviewed the Merger Agreement and
such other documents and matters of law and fact as we have considered necessary
or appropriate, and we have assumed, with your consent that: (i) the Merger will
be completed in the manner set forth in the Merger Agreement and Proxy
Statement/Prospectus and the covenants and representations described therein
will be complied with in all respects, (ii) the representations contained in the
letters of representation from the Company and Washington Mutual to us both
dated October 12, 2001 (the "Representation Letters"), will be true and complete
at the Effective Time as if made at the Effective Time and (iii) any
representations made in the Representation Letters "as of the date hereof" or
"to the best knowledge of" are true, correct and complete and will be true,
correct and complete at the Effective Time. We hereby confirm our opinion set
forth in the Joint Proxy Statement/Prospectus under the heading "THE MERGER
AGREEMENT -- Material United States Federal Income Tax Consequences of the
Merger".

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Dime Bancorp, Inc.                                                           -2-


        We hereby consent to the filing of this opinion as an exhibit to the
Joint Proxy Statement/Prospectus and the reference to us in the Joint Proxy
Statement/Prospectus under the heading "THE MERGER AGREEMENT -- Material United
States Federal Income Tax Consequences of the Merger". By giving the foregoing
consent, we do not admit that we come within the category of persons whose
consent is required under Section 7 of the Securities Act of 1933, as amended,
or the rules and regulations of the Securities and Exchange Commission
thereunder.

                                                         Very truly yours,

                                                         /s/ Sullivan & Cromwell