Serum prolactin was studied in 25 fertile and 127 infertile men. The latter included 91 oligospermic, 27 azoospermic, and 9 hypogonadotropic hypogonadal men. The mean prolactin level in all 3 groups of infertile men was significantly above that of the fertile group. There was no correlation among serum levels of follicle stimulating hormone, luteinizing hormone, sperm count, and serum prolactin values. Hyperprolactinemia was found in 5 patients (2 oligospermic, 1 azoospermic, and 2 hypogonadotropic hypogonadal men). Bromocriptine, 2.5 mg twice daily, suppressed hyperprolactinemia. In 1 man with hyperprolactinemic oligospermia, treatment with bromocriptine yielded significant improvement in sperm count (to normal values).