The purpose of this investigation was to ascertain whether estrogenic hormones in amounts above normal could be demonstrated in the urines of patients having prostatic enlargement or prostatic tumors. Estrus-producing substances occur in the male, as has been shown for the testis by Brouha and Simonnet (1) and Fellner (2); for the blood by Frank and Goldberger (3) and Hirsch (4); and for the urine by Laqueur and de Jongh (5), Loewe et al. (6), and Fee et al. (7). Other workers have observed the presence of gonadotropic hormones in the male urine, and several methods for extracting such agents have been employed, as reported by Allen et al. (8), Loewe (9), Glimm and Wadehn (10), Frank et al. (11), and Katzman and Doisy (12). A possible significance of the occurrence of gonadotropic hormones in the urines of males has been suggested by the work of Lacassagne (13), Burrows and Kennaway (14), and more recently Burrows (15) and deJongh (16). These workers have observed that injecting or painting of mice with solutions of folliculin, estrin, or ketohydroxyestrin produced a squamous keratinizing epithelium in the prostate. Prolonged administration was essential to induce this result. Burrows has discussed the possibility of hyperplasia and metaplasia in the prostates of elderly men being due to an excess of estrin in the system, inasmuch as these changes resemble the experimental changes induced in mice. In view of the small dosages employed by Burrows, there seems to be no objection to the hypothesis that an altered sex hormone balance may exist in patients suffering with prostatic enlargement or with malignant prostatic conditions. Data as presented here, however, do not indicate any greatly increased amount of the female sex hormones or of the prolans in the urines of male patients having prostatic tumors. The urinary findings cannot be compared in value to the findings noted for water-soluble estrus-producing hormones in the urines of patients suffering with teratoma testis as reported by Zondek (17), Ferguson (18), Cutler and Owen (19), or with chorionepithelioma testis as observed by Heidrich et al. (20) and Fortner and Owen (21).