<ARTICLE>                     5
<LEGEND>
This schedule contains summary financial information extracted from Swift Energy
Managed Pension Assets Partnership 1990-B, Ltd.'s balance sheet and statement of
operations contained in its Form 10-K for the year ended December 31, 1999 and
is qualified in its entirety by reference to such financial statements.
</LEGEND>

                             
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                              DEC-31-1999
<PERIOD-END>                                   DEC-31-1999
<CASH>                                         185,528
<SECURITIES>                                    0
<RECEIVABLES>                                  70,532
<ALLOWANCES>                                   0
<INVENTORY>                                    0
<CURRENT-ASSETS>                               262,952
<PP&E>                                         3,967,058
<DEPRECIATION>                                 (3,502,080)
<TOTAL-ASSETS>                                 727,930
<CURRENT-LIABILITIES>                          8,574
<BONDS>                                        0
<PREFERRED-MANDATORY>                          0
<PREFERRED>                                    0
<COMMON>                                       0
<OTHER-SE>                                     719,356
<TOTAL-LIABILITY-AND-EQUITY>                   727,930
<SALES>                                        179,994
<TOTAL-REVENUES>                               191,107
<CGS>                                          0
<TOTAL-COSTS>                                  72,913<F1>
<OTHER-EXPENSES>                               0
<LOSS-PROVISION>                               0
<INTEREST-EXPENSE>                             0
<INCOME-PRETAX>                                48,169
<INCOME-TAX>                                   0
<INCOME-CONTINUING>                            48,169
<DISCONTINUED>                                 0
<EXTRAORDINARY>                                0
<CHANGES>                                      0
<NET-INCOME>                                   48,169
<EPS-BASIC>                                    0
<EPS-DILUTED>                                  0

<FN>
<F1>Includes lease operating expenses, production taxes and depreciation and
amortization expense.  Excludes general and administrative and interest expense.
</FN>