COSTAR GROUP, INC. — Director's Dealing 2012

Aug 2, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: COSTAR GROUP INC (CSGP)
CIK: 0001057352
Period of Report: 2012-08-01

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

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-08-01	Common Stock, par value $0.01 per share	M	46448	$28.15	Acquired	365647	Direct
2012-08-01	Common Stock, par value $0.01 per share	S	56448	$80.10	Disposed	309199	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-08-01	Option to Acquire Common Stock	$28.15	M	46448	Disposed	2013-09-22	Common Stock (46448)	Direct

Footnotes

F1: Represents all shares of Common Stock owned, consisting of 175,046 shares of Common Stock and 190,601 shares of Common Stock subject to unvested Restricted Stock Grants.

F2: Average based on sales prices ranging from $79.00 to $82.61.

F3: Represents all shares of Common Stock owned, consisting of 118,598 shares of Common Stock and 190,601 shares of Common Stock subject to unvested Restricted Stock Grants.

F4: The option vested in four equal installments on September 23, 2004, September 23, 2005, September 23, 2006 and September 23, 2007.