CoStar Group Signs Nation's Largest Office Property Owner to Long-Term National Agreement

CoStar Group Signs Nation's Largest Office Property Owner to
Long-Term National Agreement
Equity Office Properties Trust Renews, Expands Multi-Market Agreement 


BETHESDA, Md., July 28  /PRNewswire-FirstCall/ -- CoStar Group, Inc.
(NASDAQ:CSGP) today announced that Equity Office Properties Trust (NYSE:EOP),
the nation's largest office building owner and manager, is extending and
expanding its relationship with CoStar under a new three-year license
agreement.

The new agreement renews services for Equity Office professionals throughout
the U.S., and provides Equity Office's headquarter office with expanded
national access to CoStar Property(R) and CoStar Tenant(R).  CoStar believes
national access to its comprehensive leasing, sales and tenant information will
give Equity Office further insight into market conditions and complex tenant
variables.

"We are pleased to grow our relationship with one of the industry's premier
office building owners," stated CoStar Group President & CEO Andrew C.
Florance.  "Equity Office is on the leading edge with regard to formulating
leasing strategies.  We believe CoStar's information can contribute to their
program development and decision making."

"CoStar's comprehensive property and tenant information gives us tremendous
insight into what is going on in the markets and in competitive properties,"
stated Tom Bakke, Senior Vice President of National Leasing & Marketing at
Equity Office.  "This information is helpful in making decisions to maximize
the income potential of available space in our properties."

Under the agreement, CoStar is providing Equity Office professionals in 23 U.S.
offices with access to CoStar Property Professional(TM), CoStar's comprehensive
database of office, industrial and retail properties, and CoStar's entire
national inventory of for-sale listings.  In addition, some Equity Office
professionals have access to CoStar Tenant, a detailed business- to-business
prospecting and analytical tool providing commercial real estate professionals
with comprehensive tenant information.

Equity Office Properties Trust is the largest real estate investment trust
(REIT) in the United States. The company owns approximately 650 properties
comprising more than 110 million square feet of office space in the country's
major metropolitan markets.

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 60 U.S. markets, London and the United Kingdom.  Based in
Bethesda, MD, the company has approximately 1,000 employees 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
assumptions, risks and uncertainties that could cause actual results to differ
materially from those expressed or implied in the forward-looking 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 period ended March 31, 2005, under the heading "Risk Factors."  In
addition to these statements, there can be no assurance that national access to
comprehensive leasing, sales and tenant information will give Equity Office
further insight into market conditions and complex tenant variables.  All
forward-looking statements are based on information available to CoStar on the
date hereof, and CoStar assumes no obligation to update such statements. 

DATASOURCE: CoStar Group, Inc.



CONTACT:  Mark A. Klionsky, Senior Vice President, of CoStar Group, Inc.,

[phone], or 



Web site:  http://www.costar.com/

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