Several studies on artificial insemination by donor (AID) semen have suggested that the gender of infants can be influenced by treatment of the women with clomiphene citrate (CC) and by the type of semen used (fresh versus cryopreserved). We conducted a 3-year prospective clinical trial to test these hypotheses. Two groups of pregnant women were evaluated. Group I (n = 130) comprised women whose ovulation was induced by CC; group II (n = 190) comprised those who conceived during spontaneous ovulatory cycles. In a total of 320 pregnancies, 55 spontaneous abortions occurred, 23.1% in group I and 13.2% in group II (P less than or equal to 0.05). Two tubal ectopic pregnancies occurred in group I. Of the 100 and 165 pregnancies carried to term in the treated and control groups, respectively, 11% and 1.8% involved twins (P less than or equal to 0.005). When only single births were considered, group I had 46.1% males in 89 term pregnancies, and group II had 60.5% males in 162 term pregnancies. Significantly more female offspring occurred in the group treated with CC (P less than or equal to 0.05). Because it is possible that a portion of the effects observed in this study were a function of cryopreservation of the AID semen, we compared data on frozen sperm with data on fresh sperm in terms of abortion, gender, and incidence of multiple births; there were no significant differences. Fertil Steril 40:481, 1983.