<SUBMISSION>
<ACCESSION-NUMBER>0001047469-04-014818
<TYPE>424B3
<PUBLIC-DOCUMENT-COUNT>1
<FILING-DATE>20040430
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>AVALONBAY COMMUNITIES INC
<CIK>0000915912
<ASSIGNED-SIC>6798
<IRS-NUMBER>770404318
<STATE-OF-INCORPORATION>MD
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>424B3
<ACT>33
<FILE-NUMBER>333-62855
<FILM-NUMBER>04770837
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>2900 EISENHOWER AVENUE
<STREET2>SUITE 300
<CITY>ALEXANDRIA
<STATE>VA
<ZIP>22314
<PHONE>7033296300
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>2900 EISENHOWER AVENUE
<STREET2>STE 300
<CITY>ALEXANDRIA
<STATE>VA
<ZIP>22314
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>AVALON BAY COMMUNITIES INC
<DATE-CHANGED>19980618
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>BAY APARTMENT COMMUNITIES INC
<DATE-CHANGED>19931208
</FORMER-COMPANY>
</FILER>
<DOCUMENT>
<TYPE>424B3
<SEQUENCE>1
<FILENAME>a2135426z424b3.htm
<DESCRIPTION>424B3
<TEXT>
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<FONT SIZE=3 ><A HREF="#04WDC1442_1">QuickLinks</A></FONT>
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<P ALIGN="RIGHT"><FONT SIZE=2><B>Filed Pursuant to Rule&nbsp;424(b)(3)<BR>
Registration No.&nbsp;333-62855  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=2><B> <A NAME="ba1442_prospectus_supplement_to_prosp__pro03973"> </A>
<A NAME="toc_ba1442_1"> </A>
<BR>    Prospectus Supplement to Prospectus dated October&nbsp;29, 1998    <BR>    <BR>    AvalonBay Communities,&nbsp;Inc.    <BR>    <BR>    482,313 Shares of Common Stock    <BR>    </B></FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This Prospectus Supplement supplements the information we provided in our October&nbsp;29, 1998 Prospectus relating to 482,313 shares of our Common Stock that
we have issued or may issue in the future when we redeem limited partnership ownership interests in Avalon DownREIT V, L.P. This Prospectus Supplement is not complete without the Prospectus, and we
have not authorized anyone to deliver or use this Prospectus Supplement without the Prospectus. </FONT></P>


<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
this Prospectus Supplement, we use some capitalized terms that we defined in the Prospectus. You should read the Prospectus to understand those terms. Unless we indicate otherwise,
the information in this Prospectus Supplement is as of March&nbsp;31, 2004. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;As
a result of the exchange of Units and the subsequent transfer of Shares by certain Selling Stockholders identified in the prospectus dated October&nbsp;29, 1998, we are providing
this Prospectus Supplement to update the table under the caption "Selling Stockholders." The information for (i)&nbsp;Stanford Baratz on the second line referenced in the table contained in such
prospectus, (ii)&nbsp;Amy Beth Baratz Irrevocable Intervivos Trust dated May&nbsp;17, 1990, Sidney Kaplan or Steve Schachtman, Trustees on the third line, (iii)&nbsp;Leonard W. Wood on the
twenty-ninth line, (iv)&nbsp;Leonard W. Wood Family Limited Partnership Grantor Trust on the thirtieth line, and (v)&nbsp;Leonard W. Wood Family Limited Partnership on the thirty-first line, is
deleted and replaced with the following information: </FONT></P>

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<TH WIDTH="39%" ALIGN="LEFT"><FONT SIZE=2>&nbsp;</FONT><BR></TH>
<TH WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TH>
<TH WIDTH="16%" ALIGN="LEFT"><FONT SIZE=2>&nbsp;</FONT><BR></TH>
<TH WIDTH="2%" ROWSPAN=4><FONT SIZE=1>&nbsp;</FONT></TH>
<TH WIDTH="20%" ROWSPAN=4 ALIGN="CENTER"><FONT SIZE=1><B>Units Owned as of<BR>
March&nbsp;31, 2004 that<BR>
may be Redeemed<BR>
for Shares of<BR>
Common&nbsp;Stock(2)</B></FONT><HR NOSHADE></TH>
<TH WIDTH="2%" ROWSPAN=3><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=3 ROWSPAN=3 ALIGN="CENTER"><FONT SIZE=1><B>Number of Shares of Common Stock Owned After Offering(1)</B></FONT><HR NOSHADE></TH>
</TR>
<TR VALIGN="BOTTOM">
<TH WIDTH="39%" ALIGN="LEFT"><FONT SIZE=1>&nbsp;</FONT><BR></TH>
<TH WIDTH="2%" ROWSPAN=3><FONT SIZE=1>&nbsp;</FONT></TH>
<TH WIDTH="16%" ROWSPAN=3 ALIGN="CENTER"><FONT SIZE=1><B>Shares of<BR>
Common Stock<BR>
Owned as of<BR>
March&nbsp;31, 2004</B></FONT><HR NOSHADE></TH>
</TR>
<TR VALIGN="BOTTOM">
<TH WIDTH="39%" ROWSPAN=2 ALIGN="LEFT"><FONT SIZE=1><B>Name<BR> </B></FONT><HR NOSHADE></TH>
</TR>
<TR VALIGN="BOTTOM">
<TH WIDTH="2%"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH WIDTH="7%" ALIGN="CENTER"><FONT SIZE=1><B>Number</B></FONT><HR NOSHADE></TH>
<TH WIDTH="2%"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH WIDTH="9%" ALIGN="CENTER"><FONT SIZE=1><B>Percent(3)</B></FONT><HR NOSHADE></TH>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD WIDTH="39%"><FONT SIZE=2>Minneapolis Jewish Federation</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="16%" ALIGN="RIGHT"><FONT SIZE=2>5,817</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="20%" ALIGN="RIGHT"><FONT SIZE=2>0</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="7%" ALIGN="RIGHT"><FONT SIZE=2>0</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="9%" ALIGN="RIGHT"><FONT SIZE=2>*</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD WIDTH="39%"><FONT SIZE=2>Community Foundation for Greater Atlanta</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="16%" ALIGN="RIGHT"><FONT SIZE=2>29,943</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="20%" ALIGN="RIGHT"><FONT SIZE=2>0</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="7%" ALIGN="RIGHT"><FONT SIZE=2>0</FONT></TD>
<TD WIDTH="2%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="9%" ALIGN="RIGHT"><FONT SIZE=2>*</FONT></TD>
</TR>
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<DL compact>
<DT style='margin-bottom:-11pt;'><FONT SIZE=2>*</FONT></DT><DD><FONT SIZE=2>Less
than one percent.
<BR><BR></FONT></DD><DT style='margin-bottom:-11pt;'><FONT SIZE=2>1.</FONT></DT><DD><FONT SIZE=2>Assumes
that all Shares issued or issuable upon redemption of Units are sold by the Selling Stockholders.
<BR><BR></FONT></DD><DT style='margin-bottom:-11pt;'><FONT SIZE=2>2.</FONT></DT><DD><FONT SIZE=2>All
Units listed in this column can be redeemed on a one-for-one basis for shares of AvalonBay Common Stock under certain conditions. If that happens, the
Selling Stockholders may offer all of these Shares by the accompanying Prospectus.
<BR><BR></FONT></DD><DT style='margin-bottom:-11pt;'><FONT SIZE=2>3.</FONT></DT><DD><FONT SIZE=2>We
calculated the percentage of ownership based on 71,467,072 shares of Common Stock that were outstanding on March&nbsp;31, 2004. </FONT></DD></DL>
<P ALIGN="CENTER"><FONT SIZE=2>The
date of this Prospectus Supplement is April&nbsp;30, 2004. </FONT></P>

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<P><br><A NAME="04WDC1442_1">QuickLinks</A><br></P><!-- TOC_BEGIN -->
<FONT SIZE=2><A HREF="#toc_ba1442_1">Prospectus Supplement to Prospectus dated October 29, 1998 AvalonBay Communities, Inc. 482,313 Shares of Common Stock</A></FONT><BR>
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