EXHIBIT 5.1

Exhibit 5.1

[letterhead of Goodwin, Procter & Hoar]


September 14, 1999

AvalonBay Communities, Inc.
2900 Eisenhower Avenue, Suite 300
Alexandria, Virginia 22314

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 sale from time to time of 3,000,000
shares of common stock, par value $.01 per share (the "Common Stock"), of
AvalonBay Communities, Inc., a Maryland corporation (the "Company"), pursuant to
the Company's Dividend Reinvestment and Stock Purchase Plan, as amended and
restated (the "Plan").

In connection with rendering this opinion, we have examined (i) the
charter of the Company, as amended to the date hereof and on file with the
Maryland State Department of Assessments and Taxation; (ii) the bylaws of the
Company, as amended to the date hereof; (iii) such records of the corporate
proceedings of the Company as we deemed material; (iv) the Registration
Statement and the exhibits thereto; and (v) such other certificates, receipts,
records and documents as we considered necessary for the purposes of this
opinion. 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 certified, photostatic or facsimile copies, the authenticity
of the originals of such copies and the authenticity of telephonic confirmations
of public officials and others. As to facts material to our opinion, we have
relied upon certificates or telephonic confirmations of public officials and
certificates, documents, statements and other information of the Company or
representatives or officers thereof.

We are attorneys admitted to the practice of law in the Commonwealth of
Massachusetts. We express no opinion concerning the laws of any jurisdictions
other than the laws of the United States of America and the Maryland General
Corporation Law, and also express no opinion with respect to the blue sky or
securities laws of any state, including Massachusetts and Maryland.

[page 2 letterhead of Goodwin, Procter & Hoar]

AvalonBay Communities, Inc.
September 14, 1999
Page 2

Based upon the foregoing, we are of the opinion that, when the Common
Stock has been issued and paid for in accordance with the terms of the Plan, the
Common Stock will be legally issued, fully paid and nonassessable.

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.

We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to us with respect to this opinion
under the heading "Validity of the Common Stock" in the Prospectus which is a
part of such Registration Statement.

Very truly yours,

/s/ Goodwin, Procter & Hoar

GOODWIN, PROCTER & HOAR LLP