<DOCUMENT>
<TYPE>EX-8.1
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<FILENAME>ex8-1.txt
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                                                                     Exhibit 8.1


[LETTERHEAD OF WILMER CUTLER PICKERING HALE AND DORR LLP]



November 18, 2004

Franklin Street Properties Corp.
401 Edgewater Place
Suite 200
Wakefield, MA  01880-6210

Re:   Certain Federal Income Tax Matters Related to Franklin Street
      Properties Corp.

Dear Ladies and Gentlemen:

      This opinion is being delivered to you in connection with certain federal
income tax matters related to Franklin Street Properties Corp. ("FSP Corp.") in
connection with the registration of shares of common stock of FSP Corp. as more
fully described in FSP Corp.'s Registration statement on Form S-3 filed with the
Securities and Exchange Commission on November 18, 2004 (the "Registration
Statement"). Except as otherwise provided, capitalized terms not defined herein
have the meanings set forth in the Registration Statement or in the letter
delivered to Wilmer Cutler Pickering Hale and Dorr LLP by FSP Corp. containing
certain representations of FSP Corp. relevant to this opinion (the
"Representation Letter"). All section references, unless otherwise indicated,
are to the United States Internal Revenue Code of 1986, as amended (the "Code").

      The conclusions expressed herein represent our judgment as to the proper
application of relevant provisions of the Code, Treasury Regulations, case law,
and rulings and other pronouncements of the Internal Revenue Service (the "IRS")
as in effect on the date of this opinion. No assurances can be given that such
laws will not be amended or otherwise changed, or that such changes will not
affect the conclusions expressed herein. Nevertheless, we undertake no
responsibility to advise you of any developments in the application or
interpretation of the income tax laws of the United States.

      Our opinion represents our best judgment of how a court would decide if
presented with the issues addressed herein and is not binding upon either the
IRS or any court. Thus, no assurances can be given that a position taken in
reliance on our opinion will not be challenged by the IRS or rejected by a
court.

      In our capacity as counsel to FSP Corp., and for purposes of rendering
this opinion, we have examined and relied upon the Registration Statement, the
Agreement and Plan of Merger dated as of August 13, 2004, by and among FSP
Corp., Montague Acquisition Corp., Addison Circle Acquisition Corp., Royal Ridge
Acquisition Corp., Collins Crossing Acquisition Corp., FSP Montague Business
Center Corp., FSP Addison Circle Corp., FSP Royal Ridge Corp., and FSP Collins

<PAGE>

November 18, 2004
Page 2


Crossing Corp. (including the exhibits thereto, the "Merger Agreement"), the
Consent Solicitation/Prospectus on Form S-4 filed by FSP Corp. with the
Securities and Exchange Commission on November 18, 2004 related to the Merger
Agreement (the "Consent Solicitation"), the Representation Letter, the Articles
of Incorporation of FSP Corp. and the Bylaws of FSP Corp., each as amended
though the date hereof, and such other documents as we considered relevant to
our analysis. In our examination of documents, we have assumed the authenticity
of original documents, the accuracy of copies, the genuineness of signatures,
and the legal capacity of signatories.

      We have made such factual and legal inquiries, including examination of
the documents set forth above, as we have deemed necessary or appropriate for
purposes of our opinion. For purposes of rendering our opinion, however, we have
not made an independent investigation or audit of the facts set forth in any of
the above-referenced documents, including the Registration Statement, the Merger
Agreement, the Consent Solicitation and the Representation Letter. We
consequently have relied upon the representations contained therein and assumed
that the information presented in such documents or otherwise furnished to us is
accurate and complete in all respects relevant to our opinion. Without limiting
the foregoing, we have not undertaken to review and determine the tax status, as
a partnership for federal income tax purposes, of each Partnership Subsidiary in
which FSP Corp. owns an interest. Instead, we have relied upon your
representations, set forth in the Representation Letter, as to the status of the
Partnership Subsidiaries for federal income tax purposes. If any one or more of
the Partnership Subsidiaries were to be classified as an association taxable as
a corporation for federal income tax purposes, and FSP Corp. were considered to
own (or have owned) more than either 10% of the voting power or 10% of the total
value of the outstanding securities of such entity, that could preclude FSP
Corp. from qualifying as a REIT for federal income tax purposes, unless (i) the
entity was wholly-owned by FSP Corp., (ii) the entity was properly classified as
a REIT, (iii) the entity was to qualify and elect to be treated as a "taxable
REIT subsidiary" under the applicable provisions of the Code, or (iv) for tax
years beginning after October 22, 2004, the relief provisions related to REITs
added by the American Jobs Creation Act of 2004 (the "2004 Tax Act") were to
apply.

      In our review, we have assumed, with your consent, that all of the
obligations imposed by any documents on the parties thereto have been and will
be performed or satisfied substantially in accordance with their terms.
Moreover, we have assumed that FSP Corp. and the Partnership Subsidiaries have
been and will continue to be operated in the manner described in the relevant
partnership agreement, articles (or certificate) of incorporation or other
organizational documents and in the Registration Statement. Finally, we have
assumed that any statement in the Representation Letter that is made "to the
knowledge of", "belief of" or similarly qualified is correct and accurate, and
that such representation or statement will continue to be correct and accurate,
without such qualification.

      We also have assumed for the purposes of this opinion, without inquiry
with respect thereto, that (i) FSP Corp is a validly organized and duly
incorporated corporation under the laws of the State of Maryland, and (ii) FSP
Corp. has not revoked the REIT election made for its taxable year ended December
31, 2002. In the event any of the statements, representations, or assumptions
upon which we have relied in rendering this opinion is incorrect or incomplete,
our opinion could be adversely affected and may not be relied upon.

<PAGE>

November 18, 2004
Page 3


Opinions

      Based upon the foregoing, and subject to the various assumptions,
limitations, and qualifications set forth in this letter, we are of the opinion
that:

      1. FSP Corp. was organized and has operated in conformity with the
requirements for qualification and taxation as a REIT under the Code for each
taxable year beginning with its taxable year ended December 31, 2002, and the
Company's current organization and method of operation (as described in the
Registration Statement and the Representation Letter) will enable the Company to
continue to meet the requirements for qualification and taxation as a REIT.

      2. To the extent that the matters discussed under the heading "Material
United States Federal Income Tax Considerations" in the Registration Statement
constitute matters of law, they are accurate in all material respects.

      FSP Corp.'s qualification and taxation as a REIT depends upon FSP Corp.'s
ability to meet on a continuing basis, through actual annual operating and other
results, the various requirements under the Code and described in the
Registration Statement with regard to, among other things, the sources of its
gross income, the composition of its assets, the level of distributions to
stockholders, and the diversity of its share ownership. Wilmer Cutler Pickering
Hale and Dorr LLP will not review FSP Corp.'s compliance with these requirements
on a continuing basis. No assurance can be given that the actual results of
operations of FSP Corp., the sources of its income, the nature of its assets,
the level of FSP Corp.'s distributions to its shareholders and the diversity of
the Company's share ownership for any given taxable year will satisfy the
requirements under the Code for qualification and taxation as a REIT or that the
relief provisions applicable to REITs including those added by the 2004 Tax Act
will be available to FSP Corp.

      FSP Corp.'s ability to qualify as a REIT also depends on it not having any
"earnings and profits" accumulated in any prior taxable year of FSP Corp. or any
of its predecessors (including the Target REITs) in which FSP Corp. or the
predecessor was a taxable "C corporation" not qualified as a REIT. FSP Corp. has
represented that it does not have and has not had at the close of any taxable
year any undistributed C corporation earnings and profits and that it will not
acquire any undistributed C corporation earnings and profits as a result of the
Mergers. Moreover, based entirely on the representations of the Target REITs in
the exhibits to the Merger Agreement, the Target REITs have operated in
conformity with the requirements for qualification and taxation as REITs since
their respective incorporations and therefore have been unable to accumulate any
earnings and profits as C corporations. Accordingly, FSP Corp. should satisfy
the "no C corporation earnings and profits" requirement, however no assurances
can be given that the IRS could not successfully challenge such position.

<PAGE>

November 18, 2004
Page 4


      This opinion addresses only the specific United States federal income tax
consequences set forth above in the numbered paragraphs under the caption
"Opinions", and does not address any other federal, state, local, or foreign
income, estate, gift, transfer, sales, use, or other tax consequences that may
be applicable to FSP Corp.

      This opinion is intended solely for the purpose of inclusion as an exhibit
to the Registration Statement. It may not be relied upon for any other purpose
and may not be made available to any other person or entity without our prior
written consent. We hereby consent to the filing of this opinion as an exhibit
to the Registration Statement and further consent to the use of our name in the
Registration Statement in connection with references to this opinion. In giving
this consent, however, we do not hereby admit that we are in the category of
persons whose consent is required under Section 7 of the Securities Act of 1933,
as amended.

                                       Very truly yours,


                                       Wilmer Cutler Pickering Hale and Dorr LLP

                                       By: /s/ Robert D. Burke
                                           -----------------------
                                       By: Robert D. Burke
<PAGE>

November 18, 2004
Page 5


                                    EXHIBIT A


Montague Acquisition Corp.
Addison Acquisition Corp.
Royal Ridge Acquisition Corp.
Collins Crossing Acquisition Corp.

<PAGE>

November 18, 2004
Page 6


                                    EXHIBIT B


FSP Montague Business Center Corp.
FSP Addison Corp.
FSP Royal Ridge Corp.
FSP Collins Crossing Corp.

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