EXHIBIT 5.1



                       [MAYER, BROWN & PLATT LETTERHEAD]



                                December 21, 2001

The Board of Trustees
ProLogis Trust
14100 East 35th Place
Aurora, Colorado  80011

         Re: ProLogis Trust Registration Statement on Form S-3

Ladies and Gentlemen:

         We have acted as special counsel to ProLogis Trust, a Maryland real
estate investment trust ("ProLogis"), in connection with the registration of up
to 49,903,814 common shares of beneficial interest, par value $0.01 per share,
of ProLogis (the "Common Shares"), as described in the Registration Statement
filed on the date hereof on Form S-3 with the Securities and Exchange Commission
under the Securities Act of 1933, as amended, (together with all amendments
thereto, the "Registration Statement").

         As special counsel to ProLogis, we have examined originals or copies,
certified or otherwise identified to our satisfaction, of ProLogis's declaration
of trust and bylaws, the resolutions of ProLogis's Board of Trustees and such of
ProLogis's records, certificates and other documents and such questions of law
as we considered necessary or appropriate for the purpose of this opinion. As to
certain facts material to our opinion, we have relied, to the extent we deem
such reliance proper, upon certificates of public officials and officers of
ProLogis. In rendering this opinion, we have assumed the genuineness of all
signatures, the authenticity of all documents submitted to us as originals and
the conformity to authentic original documents of all documents submitted to us
as copies.

         Based upon and subject to the foregoing and to the assumptions,
conditions and limitations set forth herein, we are of the opinion that the
Common Shares have been duly authorized and, when the Common Shares are issued
and sold in the manner described in the Registration Statement, will be legally
issued, fully paid and nonassessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to all references to our firm in the Registration
Statement.



The Board of Trustees
December 21, 2001
Page 2



         The opinions contained herein are limited to Federal laws of the United
States, the laws of the State of Illinois and the laws of the State of Maryland
governing real estate investment trusts. We are not purporting to opine on any
matter to the extent that it involves the laws of any other jurisdiction.

         These opinions are furnished to you solely for your benefit in
connection with the transactions described herein and are not to be used for any
other purpose without our prior written consent.

                                   Sincerely,


                                   /s/ MAYER, BROWN & PLATT

                                   Mayer, Brown & Platt