<TABLE> <S> <C>

<ARTICLE> 6
<CIK> 0000078713
<NAME> PIONEER FUND
<SERIES>
   <NUMBER> 004
   <NAME> PIONEER FUND CLASS Y
<CURRENCY> US

<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-2000
<PERIOD-END>                               JUN-30-2000
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<SENIOR-LONG-TERM-DEBT>                              0
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<SENIOR-EQUITY>                                      0
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<SHARES-COMMON-STOCK>                           211874
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<APPREC-INCREASE-CURRENT>                  (215080558)
<NET-CHANGE-FROM-OPS>                        280632618
<EQUALIZATION>                                       0
<DISTRIBUTIONS-OF-INCOME>                        36741
<DISTRIBUTIONS-OF-GAINS>                             0
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<NUMBER-OF-SHARES-SOLD>                          28600
<NUMBER-OF-SHARES-REDEEMED>                      76772
<SHARES-REINVESTED>                                733
<NET-CHANGE-IN-ASSETS>                       362000892
<ACCUMULATED-NII-PRIOR>                              0
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<GROSS-EXPENSE>                               44700992
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<PER-SHARE-NII>                                   0.18
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<PER-SHARE-DISTRIBUTIONS>                            0
<RETURNS-OF-CAPITAL>                                 0
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<EXPENSE-RATIO>                                   0.71


</TABLE>