To determine whether clomiphene citrate (CC) improves fertility in oligospermic men, 23 men with sperm concentrations between 0.5 and 20 million sperm per milliliter; normal serum gonadotropins and testosterone; and a presumptively fertile partner were enrolled in the study. After a 3-month control period, patients were randomly prescribed CC, 25 mg/day; or placebo, 1 tablet/day, for 12 months. The pregnancy rates for the CC group and the placebo group were 9.09% and 44.44%, respectively (not significant). During the treatment phase, the CC group had significantly higher levels of luteinizing hormone (LH) serum, follicle-stimulating hormone (FSH), testosterone (T), and estradiol than the placebo group. CC treatment also resulted in greater LH, FSH, and T responses to gonadotropin-releasing hormone (GnRH). There were no differences between the placebo and CC groups for the sperm penetration assay or semen parameters. The authors conclude that CC is not a useful drug in the treatment of male infertility.