CoStar Signs Jones Lang LaSalle to Long-Term Renewal; Jones Lang LaSalle Professionals To Access Leasing, Tenant Data via New CoStar Property 8.0 Platform.

Business Editors

BETHESDA, Md.--(BUSINESS WIRE)--April 21, 2003

CoStar Group Inc. (NASDAQ: CSGP) has signed a multi-year renewal agreement to provide its industry leading leasing and tenant data to Jones Lang LaSalle (NYSE:JLL) professionals in 32 offices nationwide.

CoStar Group is the leading provider of information services to commercial real estate firms in the United States and the United Kingdom. Jones Lang LaSalle is one of the premier real estate services firms, providing comprehensive management, transaction and advisory services worldwide.

"CoStar has been an effective partner supplying data and technology to help us deliver outstanding results for our clients," commented William Krouch, chief executive officer of Investment Services at Jones Lang LaSalle. "Comprehensive market data coupled with local market insights are essential components in providing strategic advice to our clients."

The multi-year agreement provides 900 Jones Lang LaSalle U.S. professionals with access to a complete inventory of office and industrial properties through CoStar Property(R). Commercial real estate professionals use CoStar Property to research leasing options, analyze market conditions, accurately value properties and position buildings in the marketplace. Under the agreement, Jones Lang LaSalle will be upgrading to CoStar Property 8.0, CoStar's enhanced, web-based platform.

In addition, Jones Lang LaSalle professionals will have access to CoStar Tenant(R), a detailed business-to-business prospecting and analytical tool providing commercial real estate professionals with the most comprehensive tenant information available.

"We're honored to continue our long association with Jones Lang LaSalle," said CoStar president & CEO Andrew C. Florance. "Jones Lang LaSalle was the first major player to standardize nationally on our information platform almost three years ago. Since that time, almost every major international brokerage firm has followed their lead."

Jones Lang LaSalle also uses CoStar Connect(R) under a separate license agreement to maintain the listing information on over 500 properties on its corporate Web site, www.am.joneslanglasalle.com. Together With CoStar Property 8.0, CoStar Connect will enable Jones Lang LaSalle professionals to share CoStar's dynamic content online with their clients via a secure "extranet" accessed through the Jones Lang LaSalle Web site.

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 products offers customers access via the Internet to the most comprehensive, verified database of commercial real estate information on 50 U.S. markets and the United Kingdom. Based in Bethesda, MD, the company has approximately 850 employees in 34 offices throughout the United States and the United Kingdom, including the largest professional research organization in the industry.

About Jones Lang LaSalle

Jones Lang LaSalle (NYSE: JLL) is the world's leading real estate services and investment management firm, operating across more than 100 markets on five continents. The company provides comprehensive integrated expertise, including management services, implementation services and investment management services on a local, regional and global level to owners, occupiers and investors. Jones Lang LaSalle is also the industry leader in property and corporate facility management services, with a portfolio of approximately 735 million square feet under management worldwide. For more information visit, www.joneslanglasalle.com.

This news release includes "forward-looking statements," which involve many risks and uncertainties that could cause actual results to differ materially from these statements. Factors that could cause or contribute to such differences include, but are not limited to, those stated in CoStar's various filings with the Securities and Exchange Commission, including Form 10-K for the year ended December 31, 2002, under the heading "Risk Factors." All forward-looking statements are based on information available to CoStar on the date hereof, and CoStar assumes no obligation to update such statements.