COSTAR GROUP, INC. — Director's Dealing 2012

Sep 6, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: COSTAR GROUP INC (CSGP)
CIK: 0001057352
Period of Report: 2012-09-04

Reporting Person: Stanfill John L (Sr. VP-Sales, Customer Service)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-09-04	Common Stock, par value $0.01 per share	F	15470	$82.45	Disposed	65223	Direct
2012-09-06	Common Stock, par value $0.01 per share	M	15000	$55.07	Acquired	80223	Direct
2012-09-06	Common Stock, par value $0.01 per share	S	34530	$81.84	Disposed	45693	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-09-06	Option to Acquire Common Stock	$55.07	M	15000	Disposed	2018-09-03	Common Stock (15000)	Direct

Footnotes

F1: Represents all shares of Common Stock owned, consisting of 22,122 shares of Common Stock and 43,101 shares of Common Stock subject to unvested Restricted Stock Grants.

F2: Represents all shares of Common Stock owned, consisting of 37,122 shares of Common Stock and 43,101 shares of Common Stock subject to unvested Restricted Stock Grants.

F3: Average based on sales prices ranging from $81.34 to $82.56.

F4: Represents all shares of Common Stock owned, consisting of 2,592 shares of Common Stock and 43,101 shares of Common Stock subject to unvested Restricted Stock Grants.

F5: The option vested in three equal installments on September 4, 2009, September 4, 2010 and September 4, 2011.