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                                                                       Exhibit 5

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

                                                                   June 21, 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. 2 on Form S-8 to
the Registration Statement on Form S-4 (File No. 33-40640) (the "Registration
Statement") of M&T Bank Corporation (the "Corporation") related to 1,349,708
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 or to be issued pursuant to the Keystone Financial,
Inc. 1992 Director Fee Plan (together, the "Plans"), plus the number of shares,
if any, that may be granted under reload rights contained in certain options
granted under the Plans:

         -     Keystone Financial, Inc. 1997 Stock Incentive Plan
         -     Keystone Financial, Inc. 1992 Stock Incentive Plan
         -     Keystone Financial, Inc. 1988 Stock Incentive Plan
         -     Keystone Financial, Inc. 1995 Non-Employee Directors' Stock
               Option Plan
         -     Keystone Financial, Inc. 1990 Non-Employee Directors' Stock
               Option Plan
         -     Financial Trust Corp Stock Option Plan of 1992
         -     Financial Trust Corp Non-Employee Director Stock Option Plan of
               1994
         -     Amended and Restated Nonqualified Stock Option Agreement with
               Donald E. Stone
         -     Elmwood Bancorp, Inc. Key Employee Stock Compensation Program

         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



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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 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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