The concentration of sex steroids in peripheral and ovarian venous blood was measured in 130 perimenopausal women. We found that the postmenopausal ovary continues to secrete a large amount of testosterone and a moderate amount of androstenedione, estrone, and dehydroepiandrosterone. Although the mean estradiol levels in the ovarian vein of postmenopausal women was low, a few subjects showed estradiol levels higher than 50 pg/ml. Postmenopausal ovaries probably continue to secrete estradiol under some endocrine conditions. These data show that the postmenopausal ovary maintains some secretory function related to estrone and estradiol. However, the endocrine effect of the postmenopausal ovary may be related to its contribution of androgens to the plasma pool of estrogens through extragonadal conversion.