Human ovarian responses to FSH- and LH-releasing hormone (FSH/LH-RH) were observed at laparotomy and studied by histologic and histochemical examination of ovarian biopsy specimens. The responses were compared to those induced by human menopausal gonadotropin (HMG) and human chorionic gonadotropin (HCG) singly and together. The subjects were healthy, fertile, young women rendered anovulatory by injections of depome-droxyprogesterone acetate (DM PA) or depochlormadinone acetate (CA). Supplementary studies included measurement of urinary pregnanediol, examination of the cervix and vagina for estrogenic and progestational responses, and endometrial biopsy. Both HMG and HCG induced follicular growth and proliferation of granulosa and theca cells, but neither, when given alone, induced ovulation or corpus luteum formation. When given in conjunction they induced single or multiple ovulations and corpora lutea in 11 of 18 women treated. FSH/LH-RH consistently stimulated follicular development and induced ovulation in 2 of 1G women treated. Preovulatory mature follicles were found in 3 more. FSH/LH-RH may prove to be useful in the treatment of some cases of anovulatory sterility of hypothalamic origin