The efficacy and safety of bromocriptine mesylate (5 to 7.5 mg per day for up to 24 weeks) were studied in 22 clinical trials involving 226 patients who had amenorrhea/galactorrhea associated with hyperprolactinemia and no demonstrable pituitary tumor. Of the 187 patients evaluated for efficacy, 80% experienced reinitiation of menses (or pregnancy without first having menses); the average treatment time (excluding those who conceived) was 5.7 weeks. Galactorrhea was significantly (at least 75%) reduced in 76% of the 187 patients after an average treatment time of 6.4 weeks, and was completely suppressed in 58% after 12.7 weeks. Maximum reduction in serum prolactin levels occurred within the first 4 weeks of therapy, and the reduced levels were maintained during treatment; moreover, there was a strong correlation between prolactin reduction and clinical improvement. Adverse reactions were reported by 68% of the 226 patients evaluated for safety; in general, these reactions were mild and transient. Several patients experienced hypotension, but only 1 discontinued therapy because of it. Based on these findings, bromocriptine mesylate was judged safe and efficacious for this purpose.