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                                                                     EXHIBIT 8.1

              MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C.
                             One Financial Center
                               Boston, MA  02111

Telephone: (617) 542-6000                              Facsimile: (617) 542-2241


                              September 20, 1999


V.I. Technologies, Inc.
155 Duryea Road
Melville, New York  11747

Ladies and Gentlemen:

     We have acted as counsel to V.I. Technologies, Inc. ("Vitex"), a Delaware
corporation, in connection with the proposed merger (the "Merger") of Pentose
Pharmaceuticals, Inc. ("Pentose"), a Delaware corporation, with and into Vitex,
pursuant to an Agreement and Plan of Merger and Reorganization (the "Merger
Agreement"), dated as of July 28, 1999, by and among Vitex, Pentose and certain
stockholders of Pentose.  The Merger is described in the Registration Statement
on Form S-4 (the "Registration Statement") of which this exhibit is a part.
This opinion is being rendered pursuant to the requirements of Item 21(a) of
Form S-4 under the Securities Act of 1933, as amended.  Capitalized terms not
defined herein have the meanings set forth in the Merger Agreement and the
documents related thereto.  All section references, unless otherwise indicated,
are to the United States Internal Revenue Code of 1986, as amended (the "Code").

     In preparing this opinion, we have examined and relied upon (i) the Merger
Agreement, (ii) the Joint Proxy Statement/Prospectus (the "Proxy Statement")
included in the Registration Statement (iii) the tax representation letters
delivered to us by Vitex and Pentose in connection with this opinion (the
"Representation Letters"), and (iv) such other documents as we have deemed
necessary or appropriate in order to enable us to render this opinion.  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.

     In rendering this opinion, we have assumed without investigation or
verification that the facts relating to the Merger as described in the Proxy
Statement are true, correct and complete in all material respects; that all
representations and warranties contained in the Proxy Statement, the Merger
Agreement and the Representation Letters are, at the time they are made, and
will remain at all times through the Effective Time, true, correct and complete
and may be relied upon by us at the time they are made and at all times through
the Effective Time; that any representation in any of the documents referred to
herein that is made "to the best of the knowledge and belief" (or similar
qualification) of any person or party are true, correct and complete without
such qualification; and that, as to all matters for which a person or entity has
represented that such person or entity is not a party to, does not have, or is
not aware of, any plan, intention, understanding or agreement, there is no such
plan, intention, understanding or agreement.  We have further assumed that all
parties to the Merger Agreement and to any other documents examined by us have
acted, and will act, in accordance with the terms of such Merger Agreement and
documents; that the Merger will be consummated at the Effective Time pursuant to
the terms and conditions set forth in the Merger Agreement (including all
covenants and conditions contained therein) without the waiver or modification
of any such terms and conditions; that the Merger will be effective as a merger
under the applicable laws of Delaware; and that Vitex and Pentose each will
comply with all reporting obligations required under the Code and Treasury
Regulations with respect to the Merger.  Any inaccuracy in, or breach of, any of
the aforementioned statements, representations or assumptions could adversely
affect our opinion.

     Our opinion is based on existing provisions of the Code, Treasury
Regulations, judicial decisions, and rulings and other pronouncements of the
Internal Revenue Service (the "IRS") as in effect on the date of this opinion,
all of which are subject to change (possibly with retroactive effect) or
reinterpretation. No assurances can be given that a change in the law on which
our opinion is based or the interpretation thereof will not occur or that such
change will not affect the opinion expressed herein. We undertake no
responsibility to advise you of any such developments in the law after the
Effective Time.
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     No ruling has been or will be sought from the IRS by Vitex or Pentose as to
the federal income tax consequences of any aspect of the Merger, and our opinion
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.

     Based upon and subject to the foregoing, the discussion contained in the
Proxy Statement under the heading "Material Federal Income Tax Consequences of
the Merger," subject to the limitations and qualifications described therein,
fairly and accurately represents our opinion as to the material United States
federal income tax consequences of the Merger.

     Our opinion addresses only the specific United States federal income tax
consequences of the Merger set forth herein, and does not address any other
federal, state, local, or foreign income, estate, gift, transfer, sales, use or
other tax consequences that may result from the Merger or any other transaction
(including any transaction undertaken in connection with the Merger).

     This opinion is being provided to you solely for use in connection with the
Registration Statement, and this opinion letter may not be used, circulated,
quoted, or otherwise referred to for any other purpose.  We hereby consent to
the use of our name under the caption "Material Federal Income Tax Consequences
of the Merger" and "Legal Matters" in the Registration Statement and to the
filing of this opinion as an exhibit to the Registration Statement.


                         Very truly yours,



                         /s/ Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
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                             Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.