0001057352-08-000036 4 1 20080427 20080429 20080429 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 Tully Christopher 0001310453 4 34 000-24531 08784705 301-215-8300 C/O COSTAR GROUP, INC. 2 BETHESDA METRO CENTER, 10TH FLOOR BETHESDA MD 20814-5388 4 1 edgar.xml PRIMARY DOCUMENT