EXHIBIT 8.1
 
                                                                  March 3, 1997
 
Softdesk, Inc.
7 Liberty Hill Road
Henniker, NH 03242
 
  Re: Merger pursuant to Agreement and Plan of Reorganization among Autodesk,
      Inc., Autodesk Acquisition Corporation, and Softdesk, Inc.
 
Ladies and Gentlemen:
 
  This opinion is being delivered to you in connection with the filing of a
registration statement (the "Registration Statement") on Form S-4, which
includes the Proxy Statement/Prospectus relating to the Agreement and Plan of
Reorganization dated as of December 10, 1996, as amended as of December 19,
1996 (the "Merger Agreement"), by and among Autodesk, Inc., a Delaware
corporation ("Autodesk"), Autodesk Acquisition Corporation, a Delaware
corporation and wholly owned subsidiary of Autodesk ("Merger Sub"), and
Softdesk, Inc., a Delaware corporation ("Softdesk"). Pursuant to the Merger
Agreement, Merger Sub will merge with and into Softdesk (the "Merger"). Except
as otherwise provided, capitalized terms not defined herein have the meanings
set forth in the Merger Agreement and the exhibits thereto or in the letters
delivered to Hale and Dorr LLP by Autodesk and Softdesk containing certain
representations of Autodesk and Softdesk relevant to this opinion (the
"Representation Letters"). All section references, unless otherwise indicated,
are to the United States Internal Revenue Code of 1986, as amended (the
"Code").
 
  In our capacity as counsel to Softdesk in the Merger, and for purposes of
rendering this opinion, we have examined and relied upon the Registration
Statement, the Merger Agreement and the exhibits thereto, the Representation
Letters, certain affiliate agreements executed in connection with the Merger,
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 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 and that the Merger will be
consummated at the Effective Time pursuant to the terms and conditions set
forth in the Merger Agreement without the waiver or modification of any such
terms and conditions. Furthermore, we have assumed that all representations
contained in the Merger Agreement, as well as those representations contained
in the Representation Letters, are, and at the Effective Time will be, true
and complete in all material respects, and that any representation made in any
of the documents referred to herein "to the best of the knowledge and belief"
(or similar qualification) of any person or party is correct without such
qualification. We have also assumed 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 not attempted to verify independently such representations, but in the
course of our representation, nothing has come to our attention that would
cause us to question the accuracy thereof.
 
  The conclusions expressed herein represent our judgment as to the proper
treatment of certain aspects of the Merger under the income tax laws of the
United States based upon 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 prior to the Effective Time, or at
any other time, or that such changes will not affect the conclusions expressed
herein. Nevertheless, we undertake no responsibility to advise you of any
developments after the Effective Time in the application or interpretation of
the income tax laws of the United States.
 
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  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.
 
  This opinion addresses only the specific United States federal income tax
consequences of the Merger set forth below 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). We express no opinion regarding the tax consequences of the Merger to
shareholders of Softdesk that are subject to special tax rules, and we express
no opinion regarding the tax consequences of the Merger arising in connection
with the ownership of options or warrants for Softdesk stock.
 
  On the basis of, and subject to the foregoing, and in reliance upon the
representations and assumptions described above, we are of the following
opinion:
 
    1. The Merger will constitute a reorganization within the meaning of
  Section 368(a);
 
    2. No gain or loss will be recognized by Autodesk, Merger Sub, or
  Softdesk as a result of the Merger;
 
    3. No gain or loss will be recognized by the shareholders of Softdesk
  upon the exchange of Softdesk stock solely for shares of Autodesk stock in
  the Merger;
 
    4. Cash received by the shareholders of Softdesk in lieu of fractional
  shares of Autodesk stock will be treated as received as a distribution in
  redemption of such fractional shares, subject to the provisions of Section
  302, as if such fractional shares had been issued in the Merger and then
  redeemed by Autodesk;
 
    5. The tax basis of the shares of Autodesk stock received by the
  shareholders of Softdesk in the Merger will be equal to the tax basis of
  the shares of Softdesk stock exchanged therefor in the Merger, reduced by
  any basis allocable to a fractional share of Autodesk stock treated as sold
  or exchanged under Section 302; and
 
    6. The holding period for the shares of Autodesk stock received by the
  shareholders of Softdesk will include the holding period for the shares of
  Softdesk stock exchanged therefor in the Merger, provided that the shares
  of Softdesk stock are held as capital assets at the Effective Time.
 
  In rendering this opinion, we have assumed that Wilson, Sonsini, Goodrich &
Rosati, P.C. has delivered, and has not withdrawn, an opinion that is
substantially similar to this one. No opinion is expressed as to any federal
income tax consequence of the Merger except as specifically set forth herein,
and this opinion may not be relied upon except with respect to the
consequences specifically discussed herein.
 
  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
or by any other person or entity, 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 and the tax consequences of the Merger. 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,
 
                                          /s/ Hale and Dorr LLP
 
                                          Hale and Dorr LLP
 
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