-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 TCKGDmnqPmc4OIkDF+mGCoNYi3X2ZGqP3csiEMROts74CT199vBcatDwwp6IeA83
 hyZjfyhc03Yt8IYchqMiSA==

<SEC-DOCUMENT>0001057352-11-000003.txt : 20110203
<SEC-HEADER>0001057352-11-000003.hdr.sgml : 20110203
<ACCEPTANCE-DATETIME>20110203125301
ACCESSION NUMBER:		0001057352-11-000003
CONFORMED SUBMISSION TYPE:	8-K
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20110202
ITEM INFORMATION:		Entry into a Material Definitive Agreement
ITEM INFORMATION:		Completion of Acquisition or Disposition of Assets
FILED AS OF DATE:		20110203
DATE AS OF CHANGE:		20110203

FILER:

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

	FILING VALUES:
		FORM TYPE:		8-K
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24531
		FILM NUMBER:		11569495

	BUSINESS ADDRESS:	
		STREET 1:		2 BETHESDA METRO CENTER
		STREET 2:		10TH FLOOR
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
		BUSINESS PHONE:		3012158300

	MAIL ADDRESS:	
		STREET 1:		2 BETHESDA METRO CENTER
		STREET 2:		10TH FLOOR
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
</SEC-HEADER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>form_8-k.htm
<DESCRIPTION>ITEMS 1.01, 2.01
<TEXT>
<html>
<head>
    <title>form_8-k.htm</title>
    <!-- Licensed to: CoStar Group, Inc. -->
    <!-- Document Created using EDGARizer 5.2.3.0 -->
    <!-- Copyright 1995 - 2009 Thomson Reuters. All rights reserved. -->
</head>

<body bgcolor="#ffffff" style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">
<div>
<hr style="MARGIN-TOP: -5px; COLOR: #000000" noshade size="4">
<hr style="MARGIN-TOP: -10px; COLOR: #000000" noshade size="1">
</div>

<div>&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 14pt; FONT-FAMILY: Times New Roman">UNITED STATES</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 14pt; FONT-FAMILY: Times New Roman">SECURITIES AND EXCHANGE COMMISSION</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Washington, D.C. 20549</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 18pt; FONT-FAMILY: Times New Roman">FORM 8-K</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">CURRENT REPORT</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Pursuant to Section 13 or 15(d) of the</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Securities Exchange Act of 1934</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Date of Report (Date of earliest event reported):&#160;&#160;February 2, 2011</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div>
<table cellpadding="0" cellspacing="0" width="100%" style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td valign="top" width="90%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 18pt; FONT-FAMILY: times new roman">COSTAR GROUP, INC.</font></div>
</td>
</tr><tr>
<td valign="top" width="90%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(Exact name of registrant as specified in its charter)</font></div>
</td>
</tr></table>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div align="left">
<table cellpadding="0" cellspacing="0" width="100%" style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td valign="top" width="33%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman; TEXT-DECORATION: underline">Delaware</font></div>
</td>
<td valign="top" width="33%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman; TEXT-DECORATION: underline">0-24531</font></div>
</td>
<td valign="top" width="34%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman; TEXT-DECORATION: underline">52-2091509</font></div>
</td>
</tr><tr>
<td valign="top" width="33%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(State or other jurisdiction <font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">of incorporation)</font></font></div>
</td>
<td valign="top" width="33%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(Commission <font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">File Number)</font></font></div>
</td>
<td valign="top" width="34%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(IRS Employer <font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">Identification No.)</font></font></div>
</td>
</tr><tr>
<td valign="top" width="33%">&#160;</td>
<td valign="top" width="33%">&#160;</td>
<td valign="top" width="34%">&#160;</td>
</tr></table>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div align="left">
<table cellpadding="0" cellspacing="0" width="100%" style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td valign="top" width="66%" style="PADDING-BOTTOM: 2px">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman; TEXT-DECORATION: underline"><font style="DISPLAY: inline">1331 L Street, NW, Washington, DC</font></font></div>
</td>
<td valign="top" width="34%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman; TEXT-DECORATION: underline"><font style="DISPLAY: inline">20005</font></font></div>
</td>
</tr><tr>
<td valign="top" width="66%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(Address of principal executive offices)</font></div>
</td>
<td valign="top" width="34%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(Zip Code)</font></div>
</td>
</tr></table>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Registrant&#8217;s telephone number, including area code:&#160;&#160;(202) 346-6500</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div>
<table cellpadding="0" cellspacing="0" width="100%" style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td valign="top" width="90%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">Not Applicable</font></div>
</td>
</tr><tr>
<td valign="top" width="90%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">(Former name or former address, if changed since last report.)</font></div>
</td>
</tr></table>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">[ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">[ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">[ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">[ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div id="PGBRK" style="MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt">
<div id="FTR">
<div id="GLFTR" style="WIDTH: 100%" align="left"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>

<div id="PN" style="PAGE-BREAK-AFTER: always; WIDTH: 100%">
<div style="WIDTH: 100%; TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: effontselection">&#160; </font></div>

<div style="WIDTH: 100%; TEXT-ALIGN: center">
<hr style="COLOR: black" noshade size="2">
</div>
</div>

<div id="HDR">
<div id="GLHDR" style="WIDTH: 100%" align="right"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Item 1.01.&#160;&#160;Entry into a Material Definitive Agreement.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt">&#160;</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">On February 2, 2011, 1331 L Street Holdings, LLC (&#8220;Holdings&#8221;), a wholly owned subsidiary of CoStar Group, Inc. (&#8220;CoStar&#8221;), and GLL L-Street 1331, LLC (&#8220;GLL&#8221;), an affiliate of Munich-based GLL Real Estate Partners GmbH, entered into a Purchase and Sale Agreement (the &#8220;Sale Agreement&#8221;) pursuant to which (i) Holdings will sell to GLL all of its interest in a 10 story, 169,429 square-foot LEED Gold certified office building located at 1331 L Street, NW (the &#8220;Building&#8221;), in downtown Washington, DC, to GLL and (ii) CoStar Realty Information, Inc. (&#8220;CoStar Realty&#8221;), a wholly owned subsidiary of CoStar, will enter into a lease with GLL&#160;to lease back a majority of the office space located at the Building, where its corporate headquarters is currently located and is expect
ed to remain.&#160;&#160;The aggregate consideration to be paid by GLL to Holdings pursuant to the Sale Agreement is $101,000,000 in cash, up to $15,000,000 of which will be withheld for additional build out and planned tenant improvements at the Building.&#160;&#160;The closing of the sale is expected to take place before the end of February 2011, subject to closing conditions and deliveries, including without limitation negotiation of construction contracts for common area improvements within the Building and customary closing conditions.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Pursuant to and upon closing of the Sale Agreement, CoStar Realty will enter into a 15-year lease, with two five-year extension options, with GLL for 149,514 square feet of office space at the Building (the &#8220;Lease&#8221;), which Lease will be effective as of June 1, 2010 and expire May 31, 2025.&#160;&#160;The initial base rent will be $38.50 per square foot of occupied space, escalating 2.5% per year commencing June 1, 2011.&#160;&#160;CoStar&#8217;s occupied space under the Lease will consist of the entire rented premises as of June 1, 2011.&#160;&#160;The effective date&#160;of the Lease will be the date as of which CoStar Realty commenced occupation of the space, June 1, 2010.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">The Sale Agreement and Lease do not affect CoStar's fourth quarter of 2010 or full year of 2010 results. The sale leaseback will likely be accounted for as an operating lease and will result in additional rent expense in 2011. The 2011 expense impact is expected to be approximately $4.5 to $5.0 million which&#160;CoStar will discuss in greater detail on its upcoming earnings conference call scheduled for February 24, 2011 at 11 a.m. EST.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Pursuant to the Sale Agreement, CoStar has agreed to guarantee timely payment and performance of Holdings&#8217; liabilities and obligations under the Sale Agreement.&#160;&#160;Further, pursuant to the Lease, CoStar will agree to guarantee payment and performance of CoStar Realty&#8217;s obligations under the Lease pursuant to a guaranty agreement to be executed upon execution of the Lease.</font></div>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Item 2.01.&#160;&#160;Completion of Acquisition or Disposition of Assets.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt">&#160;</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">The disclosure set forth above under Item 1.01 is hereby incorporated by reference into this Item 2.01.</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div id="PGBRK" style="MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt">
<div id="FTR">
<div id="GLFTR" style="WIDTH: 100%" align="left"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>

<div id="PN" style="PAGE-BREAK-AFTER: always; WIDTH: 100%">
<div style="WIDTH: 100%; TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: effontselection">2</font></div>

<div style="WIDTH: 100%; TEXT-ALIGN: center">
<hr style="COLOR: black" noshade size="2">
</div>
</div>

<div id="HDR">
<div id="GLHDR" style="WIDTH: 100%" align="right"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">SIGNATURES</font></div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 27pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.</font></div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div>
<table cellpadding="0" cellspacing="0" width="100%" style="FONT-SIZE: 10pt; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">COSTAR GROUP, INC.</font></div>
</td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">By:</font></div>
</td>
</tr><tr>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">Date: February 3, 2011</font></div>
</td>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman"><font style="TEXT-DECORATION: underline">&#160;&#160;&#160;&#160; /s/&#160;&#160;Brian J. Radecki&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; </font></font></div>
</td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">Name: Brian J. Radecki</font></div>
</td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td align="left" valign="top" width="45%">
<div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">Title:&#160;&#160;&#160;Chief Financial Officer</font></div>
</td>
</tr><tr>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
<td valign="top" width="45%"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">&#160; </font></td>
</tr></table>
</div>

<div style="DISPLAY: block; TEXT-INDENT: 0pt"><br>
</div>

<div id="PGBRK" style="MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt">
<div id="FTR">
<div id="GLFTR" style="WIDTH: 100%" align="left"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>

<div id="PN" style="PAGE-BREAK-AFTER: always; WIDTH: 100%">
<div style="WIDTH: 100%; TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: effontselection">3</font></div>

<div style="WIDTH: 100%; TEXT-ALIGN: center">
<hr style="COLOR: black" noshade size="2">
</div>
</div>

<div id="HDR">
<div id="GLHDR" style="WIDTH: 100%" align="right"><font style="DISPLAY: inline; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman">&#160; </font></div>
</div>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
