Exhibit 5
                  [Letterhead of Rosenberg & Liebentritt, P.C.]

                                  June 23, 1999

ERP Operating Limited Partnership
c/o Board of Trustees
Equity Residential Properties Trust
Two North Riverside Plaza
Suite 400
Chicago, Illinois  60606

Ladies and Gentlemen:

         We are acting as counsel to ERP Operating Limited Partnership, an
Illinois limited partnership (the "Operating Partnership"), the general partner
of which is Equity Residential Properties Trust, a Maryland real estate
investment trust (the "Company"), in connection with the Operating Partnership's
registration statement on Form S-3 (the "Registration Statement") previously
declared effective by the Securities and Exchange Commission relating to
unsecured senior debt securities in a maximum aggregate offering price of
$1,000,000,000 (the "Securities") (SEC File No. 333-45557), all of which
Securities may be offered and sold by the Operating Partnership from time to
time as set forth in the prospectus which forms a part of the Registration
Statement (the "Prospectus"), and as to be set forth in one or more supplements
to the Prospectus (each, a "Prospectus Supplement"). This opinion letter is
rendered in connection with the proposed public offering by the Operating
Partnership of (i) $300,000,000 principal amount of its 7.10% Notes due June 23,
2004 (the "Notes") as described in a Prospectus Supplement dated June 17, 1999.
This opinion letter is furnished to you at your request to enable the Operating
Partnership to continue to fulfill the requirements of Item 601(b)(5) of
Regulation S-K, 17 C.F.R. ss.229.601(b)(5), in connection with the Registration
Statement.

         For purposes of this opinion letter, we have examined copies of the
following documents:

         1.       An executed copy of the Registration Statement.

         2.       The Second Amended and Restated Declaration of Trust of the
                  Company (the "Declaration of Trust"), as certified by the
                  Secretary of the Company on the date hereof as then being
                  complete, accurate and in effect.

         3.       The Second Amended and Restated Bylaws of the Company, as
                  certified by the Secretary of the Company on the date hereof
                  as then being complete, accurate and in effect.



ERP Operating Limited Partnership
Board of Trustees
Equity Residential Properties Trust
June 23, 1999
Page 2

         4.       The Fifth Amended and Restated Agreement of Limited
                  Partnership of the Operating Partnership, certified by the
                  Secretary of the Company, as the general partner of the
                  Operating Partnership, on the date hereof as then being
                  complete, accurate and in effect.

         5.       Resolutions of the Board of Trustees of the Company, as the
                  general partner of the Operating Partnership, adopted on
                  September 13, 1996, November 14, 1997 and January 14, 1998
                  relating to the filing of the Registration Statement and
                  related matters, and by the Pricing Committee of the Board of
                  Trustees on June 17, 1999, relating to the offering of the
                  Notes, each as certified by the Secretary of the Company on
                  the date hereof as then being complete, accurate and in
                  effect.

         6.       Executed copies of the Purchase Agreement dated December 13,
                  1994, as amended, between the Operating Partnership and
                  Merrill Lynch & Co., Merrill Lynch, Pierce, Fenner & Smith
                  Incorporated ("Merrill Lynch"), and the Terms Agreement dated
                  June 17, 1999, between the Operating Partnership and Merrill
                  Lynch, Banc of America Securities LLC, Chase Securities Inc.
                  and J.P. Morgan Securities Inc. (collectively, the
                  "Underwriting Agreement").

         In our examination of the aforesaid documents, we have assumed the
genuineness of all signatures, the legal capacity of natural persons, the
accuracy and completeness of all documents submitted to us, the authenticity of
all original documents, and the conformity to authentic original documents of
all documents submitted to us as certified, telecopied, photostatic, or
reproduced copies. This opinion letter is given, and all statements herein are
made, in the context of the foregoing.

         We call your attention to the fact that our firm only requires lawyers
to be qualified to practice law in the State of Illinois and, in rendering the
foregoing opinions, we express no opinion with respect to any laws relevant to
this opinion other than the laws and regulations identified herein.

         Based upon, subject to and limited by the foregoing, we are of the
opinion that, as of the date hereof, following issuance of the Notes pursuant to
the terms of the Underwriting Agreement and receipt by the Operating Partnership
of the consideration for the Notes specified in the resolutions of the Company's
Board of Trustees and the Pricing Committee referred to above, the Notes will be
validly issued and legally binding obligations of the Operating Partnership
enforceable against the Operating Partnership in accordance with their terms,
subject to applicable bankruptcy, insolvency, reorganization, moratorium,
fraudulent transfer, or similar laws affecting creditors' rights generally from
time to time in effect and general principles



ERP Operating Limited Partnership
Board of Trustees
Equity Residential Properties Trust
June 23, 1999
Page 2

of equity (regardless of whether such enforceability is considered in a
proceeding at law or in equity) and except that a waiver of rights under any
usury law may be unenforceable.

         We assume no obligation to advise you of any changes in the foregoing
subsequent to the delivery of this opinion letter. This opinion letter has been
prepared solely for your use in connection with the filing by the Operating
Partnership of a Current Report on Form 8-K on the date of this opinion letter,
which Form 8-K will be incorporated by reference into the Registration
Statement. This opinion letter should not be quoted in whole or in part or
otherwise be referred to, nor filed with or furnished to any governmental agency
or other person or entity, without the prior written consent of this firm.

         We hereby consent (i) to be named in the Registration Statement, and in
the Prospectus, as attorneys who will pass upon the legality of the Securities
to be sold thereunder and (ii) to the filing of this opinion as an Exhibit to
the Registration Statement. In giving this consent, we do not thereby admit that
we are an "expert" within the meaning of the Securities Act of 1933, as amended.

                                      Very truly yours,

                                      ROSENBERG & LIEBENTRITT, P.C.

                                      /s/ Rosenberg & Liebentritt, P.C.