Endometrial stimulation after ACTH treatment of ovariectomized rhesus monkeys (M. mulatta) provided physiological evidence for estrogen production as a result of adrenal stimulation. In further studies, urinary estrogen excretion was evaluated by means of thin-layer and gas-liquid chromatography both before and after ACTH treatment in ovariectomized and ovariectomized adrenalectomized monkeys. Estrogens (estrone, estradiol-17[beta] and estriol) were undetectable before ACTH. Only estrone was found in the urine of ovariectomized monkeys after ACTH (80 USP units daily for 2-4 weeks).