PRESS RELEASE DETAIL


Jan 28, 2011

CoStar Group to Report Fourth Quarter and Full-Year 2010 Financial Results on February 23, 2011

WASHINGTON, Jan. 28, 2011 -- CoStar Group, Inc. (Nasdaq:CSGP), commercial real estate's leading provider of information, analytic and marketing services, will announce financial results for the fourth quarter and full year of 2010 following the market close on Wednesday, February 23, 2011. Management will conduct a conference call to discuss the fourth quarter and full-year results and the company's outlook for 2011 at 11:00 AM EST on Thursday, February 24, 2011.

Earnings Release to be Issued After Market Close on Wednesday, February 23; Conference Call to Discuss 2010 Financial Results and Outlook for 2011 Scheduled for 11:00 AM EST on Thursday, February 24

WASHINGTON, Jan. 28, 2011 -- CoStar Group, Inc. (Nasdaq:CSGP), commercial real estate's leading provider of information, analytic and marketing services, will announce financial results for the fourth quarter and full year of 2010 following the market close on Wednesday, February 23, 2011. Management will conduct a conference call to discuss the fourth quarter and full-year results and the company's outlook for 2011 at 11:00 AM EST on Thursday, February 24, 2011.

To participate in the conference call, please dial (800) 230-1093 (from the United States and Canada) or (612) 288-0329 (from all other countries) and refer to conference code 190775. To listen to the conference call over the Internet, please access the audio webcast link available in the Investors section of CoStar's web site at www.CoStar.com/investors.aspx.

An audio recording of the conference call will be available for replay approximately one hour after the call's completion and remain available for a period of time following the call. To access the recorded conference call, please dial (800) 475-6701 (from the U.S. and Canada) or (320) 365-3844 (from all other countries) using access code 190775. The webcast replay will also be available in the Investors section of CoStar's web site for a period of time following the call.

About CoStar Group, Inc.

CoStar Group (Nasdaq:CSGP) is commercial real estate's leading provider of information, analytic and marketing services. Founded in 1987, CoStar conducts expansive, ongoing research to produce and maintain the largest and most comprehensive database of commercial real estate information. Our suite of online services enables clients to analyze, interpret and gain unmatched insight on commercial property values, market conditions and current availabilities. Headquartered in Washington, DC, CoStar maintains offices throughout the U.S. and in Europe with a staff of approximately 1,500 worldwide, including the industry's largest professional research organization. For more information, visit www.costar.com.




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