The hormonal effects of estrogen and androgen were first investigated at the beginning of the twentieth century. Estrogen, which was first synthesized in the 1920s, has been shown to improve menopausal symptoms, decrease the incidence of osteoporosis, have a beneficial impact on plasma lipid profiles, probably reduce ischemic cardiovascular disease, and possibly improve cognition. In addition, retrospective studies have found a decreased incidence of Alzheimer’s disease among women receiving estrogen replacement therapy compared with those not receiving this form of postmenopausal therapy. Androgen has been written about in the medical literature since 1936, when Mocquot and Moricard described its use to relieve vasomotor symptoms in postmenopausal women. During the 1940s and 1950s numerous reports appeared in the literature describing the effectiveness of estrogen-androgen combination therapy for improving the overall feeling of well-being, energy level, libido, and quality of life for postmenopausal women. Recent studies have also shown estrogen-androgen therapy to contribute to the prevention of osteoporosis and reduce serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. Both historical data and evolving data support further evaluation of the use of estrogen-androgen replacement therapy in postmenopausal women. (Am J Obstet Gynecol 1999;180:S308-11.)