0000950133-00-002615 S-3 3 20000616 COSTAR GROUP INC 0001057352 7374 522091508 DE 1231 S-3 33 333-39490 656445 2 BETHESDA METRO CENTER 10TH FLOOR BETHESDA MD 20814 3012158300 2 BETHESDA METRO CENTER BETHESDA MD 20814 S-3 1 0001.txt REGISTRATION STATMENT EX-5.1 2 0002.txt LEGAL OPINION EX-23.1 3 0003.txt CONSENT OF INDEPENDENT AUDITORS