CoStar Announces Release of Web-Based CoStar Property; New Internet Platform Integrates Industry-Leading Data, Tools for Commercial Real Estate Professionals.

Business Editors/Hi-Tech Writers

BETHESDA, Md.--(BUSINESS WIRE)--Dec. 9, 2002

CoStar Group, Inc. (NASDAQ:CSGP), the leading provider of information services to the U.S. commercial real estate industry, today announced the release of the first Web-based version of CoStar Property(R), the industry's most widely used space inventory/availability database and analysis system.

CoStar Property, the Company's flagship service, provides commercial real estate brokers, property owners, lenders, developers and managers with a comprehensive inventory of office and industrial properties in 50 U.S. markets. An estimated 40,000 commercial real estate professionals use CoStar Property to identify available space, analyze market conditions, evaluate leasing and sale opportunities, value assets and position properties in the marketplace. CoStar Property is delivered through a new CoStar Internet platform that seamlessly integrates the Company's four subscription-based information services--CoStar Property(R), CoStar Tenant(R), CoStar COMPS(R), and CoStar Exchange(R).

CoStar introduced the first desktop version of CoStar Property in 1989. The new Internet version of CoStar Property is a major upgrade to current Windows-based versions, and represents CoStar's most significant technology development in the past several years.

"We've spent almost two years developing this new Internet platform, and we're excited to bring it to market," stated CoStar President & CEO Andrew C. Florance. "Our exceptional team of software developers has created a powerful commercial real estate information platform that maximizes the Internet's advantages of communication and connectivity while expanding the core research and reporting applications associated with CoStar."

"Our customers will notice that this new release incorporates much of their feedback and provides them with powerful technology to address their need for advanced productivity and greater control over the data," Florance added.

The new web-based version of CoStar Property provides customers with direct access to CoStar's comprehensive database, and the largest proprietary digital library of commercial real estate photographs, floor plans and 360(Degree) images. CoStar's 500-person research organization--the industry's largest--proactively tracks over 24 billion square feet of office and industrial properties nationwide. Customers will see breakthrough features, including:

-- Integration of powerful map-based technology throughout the product, including CoStar's patent-pending map-based search capabilities;

-- The ability to edit data and produce professional quality reports and presentations branded with the logos of the brokerage firm and the specific client;

-- A private, user-controlled, password-protected Extranet (or electronic `file cabinet') where brokers can share space surveys and deal-related documents online in real time with clients and/or team members;

-- New analytics and forecasting tools; and

-- Optional access to national data.

"This product represents a quantum leap beyond the technology that a brokerage firm can reasonably develop in-house" Florance noted. "It provides capabilities that significantly enhance the broker's value in the eyes of his or her clients."

"By integrating a huge volume of data -- space availabilities, comparable sales data, and market analytics -- CoStar raises the bar for all real estate information providers," commented real estate technology guru Peter Pike, president of San Francisco-based PikeNet. "Access to CoStar research provides transparency to the commercial real estate marketplace and benefits all players -- principals, agents, large firms, small firms, public entities and private investors."

The new Internet version of CoStar Property is available immediately to licensed CoStar subscribers. CoStar is conducting training sessions in multiple locations in all of its local markets throughout December to enable its clients to quickly become proficient on the new technology.

In late August, CoStar began showing the new technology to real estate rainmakers in "sneak preview" events across the country. "Thousands of commercial real estate professionals have seen our new platform and the feedback has been very positive," said Florance. "Excitement has been building in the marketplace in anticipation of today's release. Our products provide real value because they deliver substantial cost savings while enhancing productivity. Companies that had not recently considered outsourcing their research and information requirement are now asking for proposals."

Many large national real estate service providers like CB Richard Ellis and Trammell Cow Company rely on CoStar data and technology across their U.S. operations. In fact, CoStar has signed multi-year, multi-market agreements with most of the leading U.S. based global real estate service providers.

For more information on Web-based CoStar Property and other CoStar services, call 877-7-COSTAR or visit the Company's Web site at www.costar.com.

About CoStar Group, Inc.

Headquartered in Bethesda, MD, CoStar Group, Inc. (Nasdaq: CSGP), is the leading provider of information services to the U.S. commercial real estate industry. CoStar's suite of products offers customers access to the most comprehensive, verified database of commercial real estate information in 50 U.S. markets. The company has approximately 800 employees in 32 offices nationally, including the industry's largest professional research organization.

This news release includes "forward-looking statements," which involve 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 include, but are not limited to, those stated in CoStar's Form 10-Q for the quarter ended September 30, 2002 under the heading "Risk Factors." In addition, there can be no assurance that CoStar Web Property will achieve all of the benefits stated herein. All forward-looking statements are based on information available to CoStar on the date hereof, and CoStar assumes no obligation to update such statements.