<TABLE> <S> <C>

<ARTICLE> 6
<CIK> 0000862502
<NAME> SALOMON BROTHERS BALANCED FUND - CLASS O
<SERIES>
   <NUMBER> 009
   <NAME> SALOMON BROTHERS INVESTMENT SERIES FUND INC.

<S>                             <C>
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1999
<PERIOD-END>                               DEC-31-1999
<INVESTMENTS-AT-COST>                      158,739,157
<INVESTMENTS-AT-VALUE>                     164,119,458
<RECEIVABLES>                               10,449,053
<ASSETS-OTHER>                                  15,177
<OTHER-ITEMS-ASSETS>                                 0
<TOTAL-ASSETS>                             174,583,688
<PAYABLE-FOR-SECURITIES>                    11,564,674
<SENIOR-LONG-TERM-DEBT>                              0
<OTHER-ITEMS-LIABILITIES>                    7,486,833
<TOTAL-LIABILITIES>                         19,051,507
<SENIOR-EQUITY>                                      0
<PAID-IN-CAPITAL-COMMON>                   147,528,017
<SHARES-COMMON-STOCK>                          113,393
<SHARES-COMMON-PRIOR>                          115,566
<ACCUMULATED-NII-CURRENT>                      179,672
<OVERDISTRIBUTION-NII>                               0
<ACCUMULATED-NET-GAINS>                      2,444,191
<OVERDISTRIBUTION-GAINS>                             0
<ACCUM-APPREC-OR-DEPREC>                     5,380,301
<NET-ASSETS>                               155,532,181
<DIVIDEND-INCOME>                            3,007,469
<INTEREST-INCOME>                            5,748,314
<OTHER-INCOME>                                       0
<EXPENSES-NET>                               2,810,391
<NET-INVESTMENT-INCOME>                      5,945,392
<REALIZED-GAINS-CURRENT>                     5,686,848
<APPREC-INCREASE-CURRENT>                  (6,394,670)
<NET-CHANGE-FROM-OPS>                        5,237,570
<EQUALIZATION>                                       0
<DISTRIBUTIONS-OF-INCOME>                       58,854
<DISTRIBUTIONS-OF-GAINS>                        26,418
<DISTRIBUTIONS-OTHER>                                0
<NUMBER-OF-SHARES-SOLD>                          4,263
<NUMBER-OF-SHARES-REDEEMED>                     12,693
<SHARES-REINVESTED>                              6,257
<NET-CHANGE-IN-ASSETS>                    (47,707,652)
<ACCUMULATED-NII-PRIOR>                        150,615
<ACCUMULATED-GAINS-PRIOR>                    (195,011)
<OVERDISTRIB-NII-PRIOR>                              0
<OVERDIST-NET-GAINS-PRIOR>                           0
<GROSS-ADVISORY-FEES>                        1,109,398
<INTEREST-EXPENSE>                                   0
<GROSS-EXPENSE>                              3,217,294
<AVERAGE-NET-ASSETS>                         1,532,000
<PER-SHARE-NAV-BEGIN>                            13.18
<PER-SHARE-NII>                                   0.54
<PER-SHARE-GAIN-APPREC>                         (0.09)
<PER-SHARE-DIVIDEND>                              0.53
<PER-SHARE-DISTRIBUTIONS>                         0.22
<RETURNS-OF-CAPITAL>                              0.00
<PER-SHARE-NAV-END>                              12.88
<EXPENSE-RATIO>                                   0.70


</TABLE>