EXHIBIT 8.1


                         Tax Opinion of Foley Hoag LLP


                                                                January 19, 2005

Benjamin Franklin Bancorp, M.H.C.
58 Main Street
P.O. Box 309
Franklin, Massachusetts 02038-0927

      Re:   U.S. Federal Income Taxation of Conversion

Ladies and Gentlemen:

      We have acted as counsel to Benjamin Franklin Bancorp, M.H.C. ("MHC"), a
Massachusetts mutual holding company, in connection with the proposed conversion
(the "Conversion") of MHC, a Massachusetts chartered mutual holding company,
from mutual to stock form of ownership, in accordance with The Benjamin Franklin
Bancorp M.H.C. Plan of Conversion adopted by MHC's Board of Trustees on October
28, 2004 (the "Plan"). Capitalized terms used but not defined herein shall have
the meanings ascribed to them in the Plan.

      We have examined the law and such papers, including the Plan, as deemed
necessary to render these opinions. As to questions of fact material to our
opinions we have relied upon representations set forth in the Plan (including
the Exhibits), and such other documents pertaining to the transactions
contemplated by the Plan as we have deemed appropriate and necessary. As to
questions of fact material to our opinions, we have relied upon representations
of MHC contained in a letter of even date addressed to us and attached to this
letter (the "Letter of Representation"), without undertaking to verify the same
by independent investigation.

      In our examination we have assumed that (i) the transactions contemplated
by the Plan will be consummated in accordance with the terms of the Plan; (ii)
each entity that is a party to any of the documents (the "Documents") described
in the preceding paragraphs has been duly organized under the laws of its state
or country of organization, is validly existing and in good standing under such
laws, and is duly qualified and in good standing in each jurisdiction in which
it is required to be qualified to engage in the transactions contemplated by the
Documents; (iii) each such entity has full power, authority, capacity and legal
right to enter into and perform the terms of the Documents and the transactions
contemplated thereby; (iv) the copies or originals of the Documents furnished to
us are authentic (if originals) or accurate (if copies), those that are
contracts or instruments are enforceable and effective in accordance with their
terms against all parties thereto, and all signatures are genuine; (v) any
representations made in the Documents are, and will continue to be, true and
complete, and no default exists under any of the Documents; (vi) the business
and affairs of each of the entities that is a party to any of the Documents will
be conducted in accordance with the Documents and all relevant laws; (vii) no
actions will be taken, no change in any of the Documents will occur, and no
other events will occur, after the date hereof, that would have the effect of
altering the facts, Documents or



Benjamin Franklin Bancorp, M.H.C.
January 19, 2005

assumptions upon which this opinion is based; and (viii) the business reasons
for the Conversion will constitute a valid business purpose, within the meaning
of Treasury Regulation section 1.368-1(b) and (c).

      The opinions rendered herein are based upon the provisions of the Internal
Revenue Code of 1986, as amended (the "Code"), Treasury Department proposed,
temporary and final regulations, judicial decisions, and rulings and
administrative interpretations of the Internal Revenue Service (the "IRS"), as
each of the foregoing exists on the date hereof. The opinion rendered below is
not binding on the IRS or any court of law, and no assurance can be given that
legislative or administrative action or judicial decisions that differ from the
opinion rendered below will not be forthcoming. Any such differences could be
retroactive to transactions or business operations prior to such action or
decisions.

      We express no opinion as to the federal income tax consequences of the
Conversion other than those described below, if any, as to any tax consequences
under the laws of any jurisdiction other than the United States, or as to the
effect of the Conversion on prior transactions, or as to any matter not
specifically addressed below.

      Based on the foregoing, we are of opinion, as of the date hereof and under
existing law, that the Conversion will constitute or be part of a reorganization
within the meaning of section 368(a) of the Code.

      We undertake no responsibility to update or supplement our opinion. We are
furnishing this letter to you in support of the information set forth under the
heading "Tax Aspects of the Conversion and the Chart Bank Acquisition" in the
Registration Statement. We hereby consent to the filing of this opinion with the
Securities and Exchange Commission as an exhibit to the Registration Statement
and to the reference to our firm under such heading in the Registration
Statement. In giving such consent, we do not thereby admit that we are in the
category of persons whose consent is required under Section 7 of the Securities
Act of 1933, as amended. This letter is not to be used, circulated, quoted, or
otherwise referred to for any other purpose, and may not be relied upon by any
person or entity other than you, without our prior written consent. For purposes
only of compliance with Treasury Regulation Section 1.6011-4T(b)(3)(i), we
hereby agree that you (and each of your employees, representatives, or other
agents) may disclose to any and all persons, without limitation of any kind, the
tax treatment and tax structure of the Conversion and all materials of any kind,
including this opinion letter any other tax analyses, that we have provided to
you relating to such tax treatment and tax structure; provided, however, that
any such information relating to the tax treatment or tax structure must be kept
confidential to the extent necessary to comply with applicable securities laws.

                                                  Very truly yours,

                                                  Foley Hoag llp

                                                  By: /s/ Richard Schaul-Yoder
                                                      ________________________
                                                      A Partner

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