COSTAR GROUP, INC. — Director's Dealing 2011

Sep 14, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: COSTAR GROUP INC (CSGP)
CIK: 0001057352
Period of Report: 2011-09-13

Reporting Person: BONDERMAN DAVID (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-09-13	Common Stock, par value $0.01 per share	M	3000	$17.97	Acquired	276086	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-09-13	Option to Acquire Common Stock	$17.97	M	1000	Disposed	2011-09-27	Common Stock (1000)	Direct
2011-09-13	Option to Acquire Common Stock	$17.97	M	2000	Disposed	2011-09-27	Common Stock (2000)	Direct

Footnotes

F1: Represents all shares of Common Stock owned, consisting of 272,114 shares of Common Stock and 3,972 shares of Common Stock subject to unvested Restricted Stock Grants.

F2: The option vested in full on September 28, 2002.

F3: The option vested in four equal installments on September 28, 2002, September 28, 2003, September 28, 2004 and September 28, 2005.