In a previous paper1we have reported our results on animal experiments concerning the toxicity and activity of stilbestrol. We found that the close similarity of the action of natural and synthetic estrogenic substances on the female sex organs and the pituitary gland of immature, mature and castrated animals could be confirmed. Some evidence of toxicity could be observed in our animals after we administered doses of stilbestrol as low as 0.1 mg. three times a week, although the changes at higher dose levels were not as drastic and alarming as those reported by Loesser.2Clinically the drug has been used by numerous investigators of the Continent and recently also in the United States for the treatment of various ovarian disorders. While the reports on the activity of the drug in the majority of cases are very encouraging, considerable discrepancy exists with regard to the untoward symptoms observed