DC Mayor Vincent C. Gray Presents CoStar Group With 2013 Mayor's Sustainability Award

DC Mayor Vincent C. Gray Presents CoStar Group With 2013 Mayor's
Sustainability Award

Award Winners Recognized for Outstanding Commitment in Sustainable Practices

WASHINGTON, July 29, 2013 (GLOBE NEWSWIRE) -- CoStar Group, Inc.
(Nasdaq:CSGP), the primary provider of websites for commercial real estate
information, analytics and marketing services, today announced that District
of Columbia Mayor Vincent C. Gray presented a 2013 Mayor's Sustainability
Award to CoStar Group, recognizing the company for outstanding commitment in
sustainable practices.

Mayor Gray presented the awards to nine individuals, businesses and civic
organizations in a ceremony held on Thursday, July 25, 2013, at the National
Museum of Women in the Arts in Washington, DC. The Mayor was joined by
Congresswoman Eleanor Holmes Norton, U.S. EPA Regional Administrator Shawn
Garvin, District Department of the Environment (DDOE) Director Keith A.
Anderson and numerous business and community leaders. Sheila C. Johnson,
founder and CEO of Salamander Hotels and Resorts and co-owner of the
Washington Mystics, Wizards, and Capitals, served as Mistress of Ceremonies.

"It is a great honor to be recognized by Mayor Gray for our company's
dedication to sustainability," said CoStar Group Founder and CEO Andrew C.
Florance. "CoStar has a long-standing commitment to sustainable business
practices throughout our company, and also within the built environment that
our business serves. We are proud to call Washington, DC our home, and to
support the Mayor's vision for making the District a model for achieving a
healthier environment, job creation and expanded prosperity."

Since 2009, the Mayor's Sustainability Awards (previously the Mayor's
Environmental Excellence Awards) have been awarded through a competitive
selection process to recognize individuals, businesses and organizations that
are moving the District toward a more sustainable future. This year's winners
represent a range of innovative endeavors to improve the lives of residents,
the quality of our environment, and access to healthy and affordable food and
housing.

"The District is taking its place as a national and international leader in
urban sustainability, because of the innovative ideas and civic commitment of
people who care deeply about our community and our environment," said Mayor
Vincent Gray. "Our Sustainable DC Plan outlines the key challenges we face as
a community: growing jobs and our economy; ensuring health and wellness;
promoting equity and diversity; and protecting the climate and our local
environment.The actions of our award winners will ensure we meet these
challenges—they are creating a greener, healthier, and more livable city
today, and for generations to come."

Summaries and case studies on each award winner become part of an online
library of best practices in the District, which is posted on DDOE's website,
www.ddoe.dc.gov. More information on implementation of the Mayor's Sustainable
DC Plan can be found at www.sustainabledc.org.

About CoStar Group, Inc.

CoStar Group (Nasdaq:CSGP) is the primary provider of websites for commercial
real estate information, analytics 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. Through LoopNet, the Company operates the most heavily
trafficked commercial real estate marketplace online with more than 7 million
registered members. CoStar operates websites that have over 9 million unique
monthly visitors in aggregate. Headquartered in Washington, DC, CoStar
maintains offices throughout the U.S. and in Europe with a staff of
approximately 2,000 worldwide, including the industry's largest professional
research organization. For more information, visit www.costar.com.

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 based upon current
beliefs and 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 Annual Report on Form
10-K for the year ended December 31, 2012, and CoStar's Quarterly Report on
Form 10-Q for the quarter ended June 30, 2013, under the heading "Risk
Factors" in each of these filings. All forward-looking statements are based on
information available to CoStar on the date hereof, and CoStar assumes no
obligation to update such statements, whether as a result of new information,
future events or otherwise.

CONTACT: ALL INQUIRIES:
         Mark Klionsky
         (202) 623-5252
         mklionsky@costar.com
 
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