Bromocriptine and placebo were given to a group of 20 polycystic ovarian disease patients on a double-blind, crossover basis. Patients were studied for three cycles: a baseline cycle without any medication, a placebo-treated cycle, and a bromocriptine-treated cycle with multiple plasma samples taken during the different phases of the menstrual cycle. The clinical response to bromocriptine was compared with that of a placebo for the following hormones: prolactin (PRL), luteinizing hormone (LH)/follicle-stimulating hormone (FSH) ratio, testosterone, androstenedione, estradiol-17β(E2), estrone (El), and progesterone. Patients were divided into two subgroups: hyperprolactinemic (basal PRL greater than 20 ng/mL) and normoprolactinemic (basal PRL less than 20 ng/mL), and the response of both subgroups to bromocriptine was compared. Prolactin, LH/FSH ratio, testosterone, and El showed a significant drop with bromocriptine, whereas E2 significantly increased. Two out of nine amenorrheic polycystic ovarian disease patients menstruated during bromocriptine treatment, and three patients showed evidence of ovulation.