The efficacy of bromocriptine therapy was studied in 84 normoprolactinemic infertile patients. Bromocriptine (2.5-5.0 mg/day) was given for at least 1 month. Bromocriptine therapy was effective in 54 of 84 cases (64%), including 6 of 15 (40%) cases with amenorrhea, 16 of 24 cases (67%) with anovulatory cycle, 9 of 15 cases (60%) with delayed ovulation and 23 of 30 cases (77%) with luteal phase defect. Sixteen cases were able to conceive with bromocriptine alone. Twenty-five patients who did not respond to bromocriptine were treated with a combination therapy consisting of bromocriptine and clomiphene. Of the 25 cases, 14 responded to the therapy, and 6 of them were able to conceive. The response of prolactin to domperidone (10 mg, i.v.) was significantly (p less than 0.01) higher in the group responding to bromocriptine than in the nonresponding group. These results indicate that the administration of bromocriptine is an effective therapy for patients with normoprolactinemic endocrine disorders, and that domperidone may be useful in selecting the candidates for bromocriptine therapy.