<TABLE> <S> <C>

<PAGE>

<ARTICLE> 9
<LEGEND>
THIS SCHEDULE CONTAINS FINANCIAL INFORMATION EXTRACTED FROM THE CONSOLIDATED
FINANCIAL STATEMENTS OF CONNECTICUT BANCSHARES, INC. FOR THE SIX MONTHS ENDED
JUNE 30, 2000 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL
STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000

<S>                             <C>                     <C>
<PERIOD-TYPE>                   6-MOS                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-2000             DEC-31-2000
<PERIOD-START>                             JAN-01-2000             JAN-01-2000
<PERIOD-END>                               JUN-30-2000             SEP-30-2000
<CASH>                                          31,175                  40,329
<INT-BEARING-DEPOSITS>                               9                      14
<FED-FUNDS-SOLD>                                25,007                  11,318
<TRADING-ASSETS>                                     0                       0
<INVESTMENTS-HELD-FOR-SALE>                          0                       0
<INVESTMENTS-CARRYING>                         295,504                 272,970
<INVESTMENTS-MARKET>                           311,939                 293,430
<LOANS>                                        995,239               1,012,407
<ALLOWANCE>                                     11,158                  11,561
<TOTAL-ASSETS>                               1,388,227               1,380,791
<DEPOSITS>                                     918,751                 904,188
<SHORT-TERM>                                   114,778                 109,088
<LIABILITIES-OTHER>                              9,571                  10,532
<LONG-TERM>                                    114,000                 124,000
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                           112                     112
<OTHER-SE>                                     220,883                 228,370
<TOTAL-LIABILITIES-AND-EQUITY>               1,388,227               1,380,791
<INTEREST-LOAN>                                 36,734                  58,311
<INTEREST-INVEST>                                8,733                  13,668
<INTEREST-OTHER>                                     0                       0
<INTEREST-TOTAL>                                45,467                  69,979
<INTEREST-DEPOSIT>                              18,212                  24,862
<INTEREST-EXPENSE>                              21,180                  32,461
<INTEREST-INCOME-NET>                           24,287                  37,518
<LOAN-LOSSES>                                      450                     825
<SECURITIES-GAINS>                             (1,784)                   (990)
<EXPENSE-OTHER>                                 28,466                  38,467
<INCOME-PRETAX>                                (1,687)                   4,584
<INCOME-PRE-EXTRAORDINARY>                     (1,687)                   4,584
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                   (1,134)                   3,064
<EPS-BASIC>                                       0.31                    0.40
<EPS-DILUTED>                                     0.31                    0.40
<YIELD-ACTUAL>                                    7.15                    7.25
<LOANS-NON>                                      8,008                   7,544
<LOANS-PAST>                                       646                   1,661
<LOANS-TROUBLED>                                     0                       0
<LOANS-PROBLEM>                                      0                       0
<ALLOWANCE-OPEN>                                10,617                  10,617
<CHARGE-OFFS>                                      110                     126
<RECOVERIES>                                       201                     245
<ALLOWANCE-CLOSE>                               11,158                  11,561
<ALLOWANCE-DOMESTIC>                            11,158                  11,561
<ALLOWANCE-FOREIGN>                                  0                       0
<ALLOWANCE-UNALLOCATED>                         11,158                  11,561


</TABLE>