In 1938, Dodds and his co-workers1, 2 reported the synthesis of 4 :4′ dihydroxy-a :B-diethyl stilbene, a compound unrelated chemically to natural estrogens which, however, possesses estrogenic properties. The following year, numerous clinical reports3–10, 16–19 attested to the fact that, in the human being, stilbestrol was capable of relieving menopausal symptoms. However, a number of the patients developed toxic symptoms, the incidence of which seemed to vary considerably in the various series of cases reported. In a preliminary report,6 presented before the New York State Medical Society, in April, 1939, we stated that the high incidence of toxic symptoms, which accompany the use of stilbestrol, constituted a serious objection to its use clinically. In this communication, we wish to report in detail the results of our further experience with stilbestrol, supplemented by morphologic studies of the endometrium, vaginal mucosa, and gonadotropic hormone assays.