ABSTRACT: The efficacy of immunotherapy for the treatment of recurrent spontaneous abortions was tested in patients selected from the same ethnically homogeneous population of Chinese in Taiwan in whom the immunogenetics of gestational trophoblastic tumors and of recurrent spontaneous abortion had been studied. The patients, who included both primary and secondary aborters, were randomly assigned to three groups: those who were immunized with their own lymphocytes (controls) (49); those who were immunized with their husbands' lymphocytes (39); and those who were immunized with third party lymphocytes (11). The data were analyzed individually for the primary and secondary aborters and collectively for both groups combined. The number of babies born, the number of current pregnancies, and the number of recurrent abortions were not statistically significantly different between the control and the immunized groups, and a similar small number of congenital abnormalities (4–9%) occurred in both the control and immunized groups. The increase in the blocking effect for the mixed lymphocyte reaction was not related to the success of the postimmunization pregnancies. Thus, this study does not show any significant improvement in the rate of livebirths in women immunized with their husbands' lymphocytes or with third party lymphocytes compared to that in a placebo-controlled group of women.