<SEC-DOCUMENT>0001057352-16-000123-index.html : 20160426
<SEC-HEADER>0001057352-16-000123.hdr.sgml : 20160426
<ACCEPTANCE-DATETIME>20160425173849
ACCESSION NUMBER:		0001057352-16-000123
CONFORMED SUBMISSION TYPE:	DEFA14A
PUBLIC DOCUMENT COUNT:		4
FILED AS OF DATE:		20160426
DATE AS OF CHANGE:		20160425
EFFECTIVENESS DATE:		20160426

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COSTAR GROUP INC
		CENTRAL INDEX KEY:			0001057352
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-BUSINESS SERVICES, NEC [7389]
		IRS NUMBER:				522091509
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		DEFA14A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24531
		FILM NUMBER:		161590000

	BUSINESS ADDRESS:	
		STREET 1:		1331 L STREET NW
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20005
		BUSINESS PHONE:		2023466500

	MAIL ADDRESS:	
		STREET 1:		1331 L STREET NW
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20005
</SEC-HEADER>
<DOCUMENT>
<TYPE>DEFA14A
<SEQUENCE>1
<FILENAME>a2016proxystatementnoticec.htm
<DESCRIPTION>DEFA14A
<TEXT>
Document 1 - file: a2016proxystatementnoticec.htm

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>2
<FILENAME>costargroupincnoticepage1.jpg
<TEXT>
Document 2 - file: costargroupincnoticepage1.jpg

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>3
<FILENAME>costargroupincnoticepage2a01.jpg
<TEXT>
Document 3 - file: costargroupincnoticepage2a01.jpg

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>4
<FILENAME>costargroupincnoticepage3.jpg
<TEXT>
Document 4 - file: costargroupincnoticepage3.jpg

</DOCUMENT>
</SEC-DOCUMENT>