Ovarian and peripheral plasma concentrations of oestrone (E1), oestradiol (E2), androstenedione (A), testosterone (T), progesterone (P) and 17 alpha-hydroxy-progesterone (17 alpha OH-P) were assayed in 20 healthy post-menopausal women undergoing hysterectomy because of uterine fibromatosis. Significant differences were found between the ovarian and peripheral levels of E1 (P less than 0.01), E2 (P less than 0.001), A (P less than 0.01), T (P less than 0.001) and P (P less than 0.001). Analysis of the possible relationships between peripheral and ovarian levels of the six steroids considered and the patients' clinical characteristics revealed a positive correlation in only three cases, viz. between body weight and peripheral levels of E1 and E2, between E1 and E2 peripheral levels and between body weight and the E1/A ratio. The ovarian-peripheral gradient was calculated for each patient and was considered significant only if the ovarian peripheral difference exceeded the sum of each concentration multiplied by twice the maximal coefficient of variation of the assays used (12%). This gradient was significant in 75% of patients for T, in 45% for A, in 35% for E2, in 25% for E1, in 35% for P and in 30% for 17 17 alpha OH-P. Our findings confirm that circulating oestrogens in post-menopausal women originate mainly from the peripheral conversion of ovarian and adrenal androgens and that the ovary still continues to produce androgens. They also provide evidence that the ovary, at least in some post-menopausal subjects, can be a potential source of oestrogens and progestogens.