During gynecologic laparotomy both ovarian and peripheral venous blood specimens were collected simultaneously, and follicle-stimulating hormone (FSH), luteinizing hormone (LH), pregnenolone (P5), 17 alpha-hydroxypregnenolone (17 alpha-OH-P5), dehydroepiandrosterone (DHA), progesterone (P4), 17 alpha-hydroxyprogesterone (17 alpha-OH-P4), delta 4-androstenedione (delta 4-A), estradiol (E2) and 20 alpha-dihydroprogesterone (20 alpha-OH-P4) were measured in each sample by means of the radioimmunoassay technique before and after the administration of synthetic LH-releasing hormone (LH-RH). Significantly higher concentrations of P5, 17 alpha-OH-P4 and E2 during the follicular phase and that of P5, DHA, P4, 17 alpha-OH-P4 and E2 during luteal phase were observed in the ovarian than in the peripheral venous blood. During the follicular phase, P5, DHA and E2 concentrations in ovarian vein blood increased significantly following LH-RH administration. It was observed that the delta 4-steroids and E2 concentrations during the luteal phase were higher than those during the follicular phase. During the luteal phase P4, 17 alpha-OH-P4, and E2 increased after LH-RH administration. Enzymes involved in the formation of these steroids may be stimulated by the intrinsic gonadotropin caused by LH-RH administration. The difference in steroidal profiles in ovarian vein blood and response to LH-RH in follicular and luteal phase were demonstrated.