A clearer picture of the role of adrenal androgens in the etiology of breast cancer is beginning to emerge. Women who develop breast cancer in premenopausal years tend to have subnormal serum levels of adrenal androgens, while subjects who develop the disease in postmenopausal years have supranormal levels of these hormones. Androgens, by acting via the androgen receptor, oppose estrogen-stimulated cell growth in premenopausal years. In postmenopausal women, elevated adrenal androgen levels stimulate cell growth by the action of the unique adrenal androgen 5-androstene-3beta,17beta-diol, also termed hermaphrodiol, via its combination with the estrogen receptor in a hormone milieu lacking, or having low concentrations of, the classical estrogen 17beta-estradiol.