<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 three months ended March 31, 2000 and is qualified in its
entirety by reference to such financial statements.
</LEGEND>
<MULTIPLIER> 1,000

                             
<PERIOD-TYPE>                   3-MOS
<FISCAL-YEAR-END>                          DEC-31-2000
<PERIOD-END>                               MAR-31-2000
<CASH>                                          76,851
<SECURITIES>                                         0
<RECEIVABLES>                                    9,880
<ALLOWANCES>                                       993
<INVENTORY>                                          0
<CURRENT-ASSETS>                                90,695
<PP&E>                                          14,294
<DEPRECIATION>                                   2,821
<TOTAL-ASSETS>                                 204,352
<CURRENT-LIABILITIES>                           24,161
<BONDS>                                              0
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           154
<OTHER-SE>                                     159,162
<TOTAL-LIABILITY-AND-EQUITY>                   204,352
<SALES>                                              0
<TOTAL-REVENUES>                                11,372
<CGS>                                                0
<TOTAL-COSTS>                                    5,977
<OTHER-EXPENSES>                                22,090
<LOSS-PROVISION>                                   237
<INTEREST-EXPENSE>                                   0
<INCOME-PRETAX>                               (16,695)
<INCOME-TAX>                                     (565)
<INCOME-CONTINUING>                           (15,104)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                  (15,104)
<EPS-BASIC>                                     (1.06)
<EPS-DILUTED>                                   (1.06)