PRESS RELEASE DETAIL


Dec 27, 2007

CoStar Acquires Denver Information Provider

2004-09-21 2004 CoStar Acquires Denver Information Provider Acquisition of RealComp Business Expands CoStar's Coverage of Comparables Sales Transactions in Denver

2004-09-21 2004 CoStar Acquires Denver Information Provider Acquisition of RealComp Business Expands CoStar's Coverage of Comparables Sales Transactions in Denver

BETHESDA, MD -- CoStar Group, Inc. (NASDAQ: CSGP) today announced it has acquired the assets of RealComp, Inc., a Denver-based provider of local commercial real estate information. Terms of the transaction were not disclosed.

RealComp was founded by John V. Winslow in 1997 and is recognized as a leading provider of comparable sales data in Denver specializing on transactions at price points under $250,000. The acquisition adds over 5,000 records and seven years of historical comparable sales data to CoStar's database.

"RealComp has developed successful methodologies to collect information on these smaller transactions," stated CoStar President & CEO Andrew C. Florance. "This information will enable us to reach the many valuation professionals that need data on these smaller transactions while enhancing the value we provide to our existing CoStar COMPS® customers. In addition, we believe RealComp's methodology will lead to efficiency gains in other markets as well, while improving our market coverage and timeliness."

CoStar is adding 32 new clients in Denver via the acquisition. CoStar now has over 265 client firms in Denver, including 17 of the top 20 brokerage firms.

About CoStar Group, Inc.

CoStar Group, Inc., (NASDAQ: CSGP) is the leading provider of information services to commercial real estate professionals in the United States and the United Kingdom. CoStar's suite of services offers customers access via the Internet to the most comprehensive database of commercial real estate information on over 55 U.S. markets, London and the United Kingdom. Based in Bethesda, MD, the company has approximately 900 employees in 38 offices throughout the United States and the United Kingdom, including the largest professional research organization in the industry.

This news release includes "forward-looking statements" including, without limitation, statements regarding CoStar's expectations, beliefs, intentions or strategies regarding the future. These statements are subject to many risks and uncertainties that could cause actual results to differ materially from these statements. More information about potential factors that could cause actual results to differ materially from those discussed in the forward-looking statements include, but are not limited to, those stated in CoStar's filings from time to time with the Securities and Exchange Commission, including CoStar's Form 10-Q for the quarter ended June 30, 2004, under the heading "Risk Factors." In addition to these statements, there can be no assurance that the acquisition of RealComp's business will enable CoStar to reach valuation professionals that need data on smaller transactions, enhance the value CoStar provides to its existing CoStar COMPS® customers, lead to efficiency gains in markets other than Denver, or improve CoStar's market coverage and timeliness. All forward-looking statements are based on information available to CoStar on the date hereof, and CoStar assumes no obligation to update such statements.
'