PROSPECTUS SUPPLEMENT
(TO PROSPECTUS DATED SEPTEMBER 14, 1999)                                        [LOGO]



                                                               Filed Pursuant to
                                                                  Rule 424(b)(2)
                                                              Reg. No. 333-87063

                                3,000,000 SHARES

                          AVALONBAY COMMUNITIES, INC.

                                  COMMON STOCK
                               ------------------

                 DIVIDEND REINVESTMENT AND STOCK PURCHASE PLAN
                               ------------------

    Effective immediately, we have modified our Dividend Reinvestment and Stock
Purchase Plan. You will continue to be able to purchase newly issued shares of
our common stock directly from us with reinvested cash dividends at a purchase
price per share equal to 97% of the last reported sale price for a share of our
common stock as reported by the New York Stock Exchange on the applicable
investment date. However, for shares purchased with optional cash payments, we
have modified the plan in the following ways:

    - The purchase price for newly issued shares of our common stock that you
      purchase directly from us with optional cash payments of up to $100,000
      per calendar quarter will be 100% of the last reported sale price for a
      share of our common stock as reported by the NYSE on the applicable
      investment date.

    - The purchase price for shares of our common stock that you purchase
      directly from us with optional cash payments in excess of $100,000 per
      calendar quarter made with a Request for Waiver will be 100% of the
      average of the daily high and low sales prices of our common stock on the
      NYSE for the ten trading days immediately preceding the applicable
      investment date.

    We previously sent to you, or are concurrently sending to you, the
prospectus to which this prospectus supplement relates. You should carefully
read this prospectus supplement together with the prospectus. In particular, you
should note that the cover page, the summary and questions 2, 11 and 22 of the
prospectus dated September 14, 1999 are hereby modified to reflect the terms set
forth above in this prospectus supplement. In all other respects, the plan will
continue to operate as it has in the past. If you would like another copy of the
prospectus or an Authorization Form, please contact our plan administrator at
the following address:

                               First Union National Bank
                               Attention: Shareholder Services Group
                               1525 West W.T. Harris Boulevard, 3C3
                               Charlotte, North Carolina 28288-1153
                               You may call First Union at (800) 829-8432.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS SUPPLEMENT OR THE RELATED PROSPECTUS.
ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

          THE DATE OF THIS PROSPECTUS SUPPLEMENT IS DECEMBER 17, 1999.