<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
This schedule contains summary financial information extracted from the
financial statements of National Surgery Centers for the periods ended
March 31, 1997, June 30, 1997 and September 30, 1997 and is qualified in
its entirety by reference to such financial statements.
</LEGEND>
<RESTATED> 
       
<S>                             <C>                     <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   6-MOS                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1997
<PERIOD-START>                             JAN-01-1997             JAN-01-1997             JAN-01-1997
<PERIOD-END>                               MAR-31-1997             JUN-30-1997             SEP-30-1997
<CASH>                                      13,472,000              12,730,000              13,995,000
<SECURITIES>                                35,110,000              25,029,000              13,368,000
<RECEIVABLES>                               15,343,000              18,563,000              22,715,000
<ALLOWANCES>                                 1,880,000               2,774,000               4,555,000
<INVENTORY>                                  2,614,000               3,130,000               3,577,000
<CURRENT-ASSETS>                            66,222,000              58,546,000              51,364,000
<PP&E>                                      45,584,000              49,132,000              52,804,000
<DEPRECIATION>                              12,012,000              13,303,000              14,720,000
<TOTAL-ASSETS>                             142,867,000             151,144,000             165,329,000
<CURRENT-LIABILITIES>                        7,386,000               9,369,000              10,447,000
<BONDS>                                      6,935,000               8,651,000              11,318,000
<PREFERRED-MANDATORY>                                0                       0                       0
<PREFERRED>                                          0                       0                       0
<COMMON>                                       120,000                 121,000                 183,000
<OTHER-SE>                                 120,600,000             124,424,000             132,206,000
<TOTAL-LIABILITY-AND-EQUITY>               142,867,000             151,144,000             165,329,000
<SALES>                                     22,116,000              46,362,000              73,295,000
<TOTAL-REVENUES>                            22,116,000              46,362,000              73,295,000
<CGS>                                       16,901,000              34,622,000              54,455,000
<TOTAL-COSTS>                               16,901,000              34,622,000              54,455,000
<OTHER-EXPENSES>                               901,000               2,027,000               3,771,000
<LOSS-PROVISION>                                     0                       0                       0
<INTEREST-EXPENSE>                             153,000                 346,000                 688,000
<INCOME-PRETAX>                              4,161,000               9,367,000              14,381,000
<INCOME-TAX>                                 1,550,000               3,489,000               5,369,000
<INCOME-CONTINUING>                          2,611,000               5,878,000               9,012,000
<DISCONTINUED>                                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0
<CHANGES>                                            0                       0                       0
<NET-INCOME>                                 2,611,000               5,878,000               9,012,000
<EPS-PRIMARY>                                      .15                     .33                     .50
<EPS-DILUTED>                                      .14                     .31                     .48
        

</TABLE>