[ARTICLE] 6
[CIK] 0000880583
[NAME] THE TRAVELERS SERIES TRUST
[SERIES]
   [NUMBER] 18
   [NAME] MFS MID CAP GROWTH PORTFOLIO
<TABLE>
<S>                             <C>
[PERIOD-TYPE]                   6-MOS
[FISCAL-YEAR-END]                          DEC-31-1999
[PERIOD-END]                               JUN-30-1999
[INVESTMENTS-AT-COST]                       31,237,553
[INVESTMENTS-AT-VALUE]                      34,544,556
[RECEIVABLES]                                   40,527
[ASSETS-OTHER]                                  27,178
[OTHER-ITEMS-ASSETS]                                 0
[TOTAL-ASSETS]                              34,612,261
[PAYABLE-FOR-SECURITIES]                       152,585
[SENIOR-LONG-TERM-DEBT]                              0
[OTHER-ITEMS-LIABILITIES]                       44,138
[TOTAL-LIABILITIES]                            196,723
[SENIOR-EQUITY]                                      0
[PAID-IN-CAPITAL-COMMON]                    29,688,905
[SHARES-COMMON-STOCK]                        3,033,924
[SHARES-COMMON-PRIOR]                        1,316,229
[ACCUMULATED-NII-CURRENT]                     (34,065)
[OVERDISTRIBUTION-NII]                               0
[ACCUMULATED-NET-GAINS]                      1,435,695
[OVERDISTRIBUTION-GAINS]                             0
[ACCUM-APPREC-OR-DEPREC]                     3,307,003
[NET-ASSETS]                                34,415,538
[DIVIDEND-INCOME]                               14,879
[INTEREST-INCOME]                               55,512
[OTHER-INCOME]                                       0
[EXPENSES-NET]                                 104,456
[NET-INVESTMENT-INCOME]                       (34,065)
[REALIZED-GAINS-CURRENT]                     1,597,595
[APPREC-INCREASE-CURRENT]                    2,252,295
[NET-CHANGE-FROM-OPS]                        3,815,825
[EQUALIZATION]                                       0
[DISTRIBUTIONS-OF-INCOME]                            0
[DISTRIBUTIONS-OF-GAINS]                       130,585
[DISTRIBUTIONS-OTHER]                                0
[NUMBER-OF-SHARES-SOLD]                      1,705,902
[NUMBER-OF-SHARES-REDEEMED]                        480
[SHARES-REINVESTED]                             12,273
[NET-CHANGE-IN-ASSETS]                      21,181,725
[ACCUMULATED-NII-PRIOR]                              0
[ACCUMULATED-GAINS-PRIOR]                     (13,315)
[OVERDISTRIB-NII-PRIOR]                              0
[OVERDIST-NET-GAINS-PRIOR]                           0
[GROSS-ADVISORY-FEES]                           89,282
[INTEREST-EXPENSE]                                   0
[GROSS-EXPENSE]                                124,852
[AVERAGE-NET-ASSETS]                        21,052,757
[PER-SHARE-NAV-BEGIN]                            10.05
[PER-SHARE-NII]                                 (0.02)
[PER-SHARE-GAIN-APPREC]                          01.35
[PER-SHARE-DIVIDEND]                                 0
[PER-SHARE-DISTRIBUTIONS]                        00.04
[RETURNS-OF-CAPITAL]                                 0
[PER-SHARE-NAV-END]                              11.34
[EXPENSE-RATIO]                                  01.00
[AVG-DEBT-OUTSTANDING]                               0
[AVG-DEBT-PER-SHARE]                                 0
</TABLE>