<ARTICLE> 5
<LEGEND>
The schedule contains summary financial information extracted from the
consolidated balance sheet and statement of operations of COSTAR GROUP, INC. as
of and for the six months ended June 30, 2000 and is qualified in its entirety
by reference to such financial statements.

<MULTIPLIER> 1,000

                             
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-2000
<PERIOD-END>                               JUN-30-2000
<CASH>                                          64,258
<SECURITIES>                                         0
<RECEIVABLES>                                    9,094
<ALLOWANCES>                                     1,482
<INVENTORY>                                          0
<CURRENT-ASSETS>                                73,530
<PP&E>                                          20,517
<DEPRECIATION>                                   3,371
<TOTAL-ASSETS>                                 181,555
<CURRENT-LIABILITIES>                           22,213
<BONDS>                                              0
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           154
<OTHER-SE>                                     146,182
<TOTAL-LIABILITY-AND-EQUITY>                   181,555
<SALES>                                              0
<TOTAL-REVENUES>                                25,944
<CGS>                                                0
<TOTAL-COSTS>                                   13,707
<OTHER-EXPENSES>                                43,661
<LOSS-PROVISION>                                   726
<INTEREST-EXPENSE>                                   0
<INCOME-PRETAX>                               (31,424)
<INCOME-TAX>                                   (1,410)
<INCOME-CONTINUING>                           (28,237)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                  (28,237)
<EPS-BASIC>                                     (1.91)
<EPS-DILUTED>                                   (1.91)