Plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH), prolactin (PRL), estradiol (E2), progesterone (P), testosterone (T), and dihydrotestosterone (DHT) were measured by radioimmunoassay in 7 patients who had ovulation induction with clomiphene citrate and human chorionic gonadotropin. Six of the 7 patients ovulated. There was higher increase in FSH than LH in 3 patients who also showed a midcycle FSH and LH peak. Plasma PRL was initially elevated in 2 patients, remained normal (less than 25 ng/ml) throughout the cycle in one patient, and showed an increase in the late luteal phase in 3 patients. Plasma E2 showed a good response at the end of clomiphene intake, with a subsequent preovulatory surge. Plasma P increased to more than 25 ng/ml in patients who ovulated and reached higher levels than in normal ovulatory cycles. Plasma T increased and decreased in a similar pattern to plasma E2 and was higher with clomiphene therapy than in the normal menstrual cycle. Plasma DHT remained similar to concentrations found in normal menstrual cycles. The findings are discussed in relation to the effect of clomiphene and these hormones on the pituitary-ovarian axis, ovulation rate, and conception rate.