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                                                                       Exhibit 5

                              M&T Bank Corporation
                                  One M&T Plaza
                             Buffalo, New York 14203

                                                               February 13, 2001
Board of Directors
M&T Bank Corporation
One M&T Plaza
Buffalo, New York 14203

Ladies and Gentlemen:

        Reference is made to the Post-Effective Amendment No. 1 on Form S-8 to
the Registration Statement on Form S-4 (File No. 33-48946) (the "Registration
Statement") of M&T Bank Corporation (the "Corporation") related to 224,800
shares of the Corporation's common stock, par value $0.50 per share ("Common
Stock"), which are to be offered pursuant to stock options granted under the
following stock option plans (the "Plans"), plus the number of shares, if any,
that may be granted under reload rights contained in certain options granted
under the Plans:

        -       Progressive Bank, Inc. Incentive Stock Option Plan Amended and
                Restated

        -       Progressive Bank, Inc. 1993 Non-Qualified Stock Option Plan for
                Directors

        -       Premier National Bancorp, Inc. 1995 Incentive Stock Plan (as
                amended and restated effective May 13, 1999)

        I have been requested to furnish an opinion to be included as Exhibit 5
to the Registration Statement. In conjunction with the furnishing of this
opinion, I have examined such corporate documents and have made such
investigation of matters of fact and law as I have deemed necessary to render
this opinion.

        I am admitted to practice law in the State of New York and do not
purport to be an expert on or to express any opinion on any laws other than the
laws of the State of New York and the federal laws of the United States of
America. This opinion speaks as of today's date and is limited to present
statutes, regulations and judicial interpretations. In rendering this opinion, I
assume no obligation to revise or supplement this opinion should the present
laws be changed by legislative or regulatory action, judicial decision or
otherwise.

        Based upon such examination and investigation, and upon the assumptions
that there will be no material changes in the documents examined and matters
investigated and that at the time



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of issuance there will be authorized but unissued shares of Common Stock
available to the Corporation in sufficient amounts, I am of the opinion that the
shares of Common Stock referred to above have been duly authorized by the
Corporation and that, when issued in accordance with the terms of the Plans,
will be legally issued, fully paid and non-assessable. I consent to the filing
of this opinion as Exhibit 5 to the Registration Statement.

        This letter does not address any matters other than those expressly
addressed herein. This letter is given for your sole benefit and use. No one
else is entitled to rely hereupon.



                                       Very truly yours,

                                       /s/ Richard A. Lammert

                                       Richard A. Lammert
                                       Senior Vice President and General Counsel




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