0001057352-08-000074 4 1 20080904 20080904 20080904 COSTAR GROUP INC 0001057352 7389 522091509 1231 2 BETHESDA METRO CENTER 10TH FLOOR BETHESDA MD 20814 3012158300 2 BETHESDA METRO CENTER 10TH FLOOR BETHESDA MD 20814 KLEIN MICHAEL R 0001066062 4 34 000-24531 081057408 WILMER, CUTLER & PICKERING 2445 M STREET NW WASHINGTON DC 20037-1420 202-689-1240 2001 K STREET, N.W. SUITE 206 WASHINGTON DC 20006 4 1 edgar.xml PRIMARY DOCUMENT