1. Vitamin A deficiency alone in the white rat is associated with atrophy of the testis and accessory sexual glands. This would appear to be indicative of some disturbance in the hypophyseal-gonadalprostatic hormonal relationships. All of the known vitamins necessary for the rat, except vitamin A, were present in the diet fed the animals studied. 2. Vitamin A deficiency in the rat is associated with foci of inflammation and epithelial metaplasia in the prostatic acini and vesicular ducts entirely similar to that reported in other organs. 3. Focal metaplasia and inflammation is occasionally encountered in the prostate of patients with extreme inanition associated with stenosis of the esophagus. It seems probable that this lesion is due to vitamin A deficiency.