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                                                                     EXHIBIT 5.1

            [Liddell, Sapp, Zivley, Hill & LaBoon, L.L.P. Letterhead]



                                  May 14, 1998



American Industrial Properties REIT
6210 N. Beltline Road
Suite 170
Irving, Texas   75063

         Re:    Legality of Securities to be Registered Under Registration
                Statement on Form S-3

Ladies and Gentlemen:

         This opinion is furnished in connection with the registration on Form
S-3 (the "Registration Statement"), pursuant to the Securities Act of 1933, as
amended, (the "Securities Act"), of the offering and sale of up to 5,910,263
Common Shares of Beneficial Interest, par value $0.10 per share (the "Shares"),
of American Industrial Properties REIT, a Texas real estate investment trust
(the "Trust"), by (i) Praedium II Industrial Associates LLC; (ii) USAA Real
Estate Trust; (iii) USAA Investors I, Inc.; (iv) USAA Investors II, Inc.; (v)
USAA Properties III, Inc.; (vi) USAA Properties IV, Inc.; (vii) MS Real Estate
Special Situations, Inc.; (viii) Morgan Stanley Asset Management Inc. ; (ix)
ABKB/LaSalle Securities Limited Partnership; and (x) LaSalle Advisers Capital
Management, Inc., or by pledgees, donees, transferees or other successors in
interest thereto (collectively, the "Selling Shareholders").

         We have examined and are familiar with originals or copies, certified
or otherwise identified to our satisfaction, of such documents, Trust records,
certificates of public officials and other instruments as we have deemed
necessary or advisable in connection with this opinion, including (a) the Third
Amended and Restated Declaration of Trust of the Trust and the Fifth Amended and
Restated Bylaws of the Trust, as amended to date, (b) minutes of the proceedings
of the Trust Managers of the Trust, and (c) the Registration Statement. In our
examination, we have assumed the genuineness of all signatures, the legal
capacity of natural persons, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as certified or photostatic copies, the authenticity of the originals of such
copies and the authenticity of telegraphic or telephonic confirmations of public
officials and others. As to facts material to our




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American Industrial Properties REIT
May 14, 1998
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opinion, we have relied upon certificates or telegraphic or telephonic
confirmations of public officials and certificates, documents, statements and
other information of the Trust or representatives or officers thereof.

         The opinions set forth herein are subject to the qualification that we
are admitted to practice law in the State of Texas and we express no opinion as
to laws other than the law of the State of Texas and the federal law of the
United States of America.

         Based upon the foregoing, we are of the opinion that the Shares, when
sold by the Selling Shareholders, will be validly issued, fully paid and
non-assessable.

         The foregoing assumes that all requisite steps will be taken to comply
with the requirements of the Securities Act and applicable requirements of state
laws regulating the offer and sale of securities, as to which we express no
opinion.

         This opinion is based upon currently existing statutes, rules and
regulations and judicial decisions and is rendered as of the date hereof, and we
disclaim any obligation to advise you of any change in any of the foregoing
sources of law or subsequent developments in law or changes in facts or
circumstances which might affect any matters or opinions set forth herein.

         We hereby consent to being named as counsel to the Trust in the
Registration Statement, to the references therein to our firm under the caption
"Legal Matters" and to the inclusion of this opinion as an exhibit to the
Registration Statement. We are furnishing this letter to you in connection with
the filing of the Registration Statement and consent to the filing of this
opinion as an exhibit to the Registration Statement. This opinion is not to be
used, circulated, quoted or otherwise referred to for any other purpose.

                             Very truly yours,

                             /s/ Liddell, Sapp, Zivley, Hill & LaBoon, L.L.P.

                             LIDDELL, SAPP, ZIVLEY, HILL & LABOON, L.L.P.