ABSTRACT: Women experiencing recurrent spontaneous abortion have a higher frequency of infertility than that expected in the general population. To further define the relationships between infertility and spontaneous abortion, the obstetrical histories of 43 women with unexplained secondary infertility were evaluated for the frequency of spontaneous abortion. Of the 88 pregnancies studied, 39 (44%) resulted in spontaneous abortion. Women with unexplained secondary infertility experienced a three-fold increase (P < 0.0001) in the frequency of spontaneous abortions and half the number of live births (P < 0.0001) compared with the general population. We conclude that the association between infertility and spontaneous abortion includes a higher frequency of spontaneous abortion among infertile couples as well as a higher prevalence of infertility among recurrent spontaneous aborters compared with the general population.