This report concerns the evaluation of various estrogens, estrone (E(1)), estradiol(E(2)), and estrone sulfate (E(1)S), as well as E(1)S-sulfatase and aromatase activities in pre- and postmenopausal women with breast cancer. The levels (in picomoles per g; mean +/- SEM) of the various estrogens in the breast tissue from premenopausal patients (n = 11) are: E(1), 1.4 +/- 0.5; E(1)S, 1.2 +/- 0.6; and E(1)S, 1.2 +/- 0.3. In postmenopausal patients (n = 23), the values are, respectively, 1.0 +/- 0.4, 1.4 +/- 0.7, and 3.3 +/- 1.9. These concentrations of estrogens in the tumors of postmenopausal patients are significantly higher than those found in plasma. The activity of E(1)S-sulfatase in both pre- and postmenopausal patients was 50-200 times higher than that of aromatase. E(1)S-sulfatase and aromatase activities are significantly higher in postmenopausal than in cycling patients. It is concluded that despite the low levels of circulating estrogens in postmenopausal patients, the tissue concentrations of these steroids are several-fold higher than those in plasma, suggesting tumor accumulation of these estrogens. The physiopathology and clinical significance of these high levels of the various estrogens (E(1) E(2), and E(1)S) as Nell as sulfatase and aromatase activities in postmenopausal patients with breast cancer is yet to be explored.