The concentrations of testosterone (T), androstenedione (A), estradiol (E2), and estrone (E1) were measured in peripheral and ovarian venous serum obtained at the time of bilateral oophorectomy from 15 postmenopausal women with endometrial cancer and 9 without cancer. The cancer and noncancer (control) patients were matched for age, weight, and years since menopause. In women with endometrial cancer, significantly higher ovarian than peripheral venous concentrations were found for all hormones measured [T, 3781 +/- 1255 (+/- SE) vs. 213 +/- 43 pg/ml (P less than 0.01); A, 5352 +/- 1845 vs. 1299 +/- 187 pg/ml (P less than 0.04); E2, 52 +/- 11 vs. 23 +/- 3 pg/ml (P less than 0.02); E1, 81 +/- 12 vs. 32 +/- 2 pg/ml (P less than 0.001)], but in the control patients, only the concentration of T was significantly higher (623 +/- 108 vs. 156 +/- 21 pg/ml; P less than 0.001). Ovarian venous concentrations of T and A were significantly higher in thin women with cancer than in obese women with cancer. These results suggest that the ovaries of postmenopausal women with endometrial cancer secrete significantly more T and A than do the ovaries of women without cancer, while secreting only minimal amounts of E2 and E1. This increase in ovarian steroid secretion might play a role in the pathogenesis of endometrial cancer.