Item 8.01. Other Events

CoStar Realty Information, Inc., a wholly owned subsidiary of CoStar Group, Inc. ("CoStar"), acquired all of the outstanding capital stock of Resolve Technology, Inc., a Delaware corporation ("Resolve Technology"), from its sole stockholder, Eric Forman, on October 19, 2009, pursuant to a Stock Purchase Agreement for approximately $3.4 million in cash and 25,886 shares of CoStar restricted common stock at closing, which shares are subject to a three-year lockup period. The purchase price is subject to certain post-closing adjustments. Additionally, the acquisition includes (i) a potential deferred payout two years after closing based on the incremental growth of Resolve Technology's revenue, and (ii) other potential deferred payouts for successful completion of additional operational and sales milestones. Resolve Technology has estimated 2009 revenue of approximately $3.6 million. The acquisition is not expected to significantly affect CoStar's 2009 revenue and earnings.

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