COSTAR GROUP, INC. — Director's Dealing 2013

Mar 18, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: COSTAR GROUP INC (CSGP)
CIK: 0001057352
Period of Report: 2013-03-14

Reporting Person: FLORANCE ANDREW C (Director, President and CEO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-03-14	Common Stock, par value $0.01 per share	M	30000	$39.00	Acquired	325449	Direct
2013-03-14	Common Stock, par value $0.01 per share	S	30000	$99.68	Disposed	295449	Direct
2013-03-15	Common Stock, par value $0.01 per share	M	20000	$39.00	Acquired	315449	Direct
2013-03-15	Common Stock, par value $0.01 per share	S	26253	$100.14	Disposed	289196	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-03-14	Option to Acquire Common Stock	$39.00	M	30000	Disposed	2014-02-28	Common Stock (30000)	Direct
2013-03-15	Option to Acquire Common Stock	$39.00	M	20000	Disposed	2014-02-28	Common Stock (20000)	Direct

Footnotes

F1: Represents all shares of Common Stock owned, consisting of 123,815 shares of Common Stock and 201,634 shares of Common Stock subject to unvested Restricted Stock Grants.

F2: Average based on sales prices ranging from $99.23 to $100.77.

F3: Represents all shares of Common Stock owned, consisting of 93,815 shares of Common Stock and 201,634 shares of Common Stock subject to unvested Restricted Stock Grants.

F4: Represents all shares of Common Stock owned, consisting of 113,815 shares of Common Stock and 201,634 shares of Common Stock subject to unvested Restricted Stock Grants.

F5: Average based on sales prices ranging from $99.34 to $100.90.

F6: Represents all shares of Common Stock owned, consisting of 87,562 shares of Common Stock and 201,634 shares of Common Stock subject to unvested Restricted Stock Grants.

F7: The option vested in four equal installments on March 1, 2005, March 1, 2006, March 1, 2007 and March 1, 2008.