The rodent vaginal epithelium is of special interest as a target organ for studying the interaction of endocrine and dietary factors. One of the earliest and most reliable manifestations of a deficiency of vitamin A is the continued cornification of the vaginal epithelium in the rat. Similarly, the rodent vaginal epithelium undergoes marked keratinization and stratification under the influence of estrogenic stimulation.Little is known regarding the basic factors underlying normal and abnormal vaginal cornification. Sherwood et al. ('36, '37) reported that oral administration of large doses of carotene suppressed the estrous vaginal smear picture in the normal rat. However, excessive doses of vitamin A administered orally (Burrill and Greene, '41) or subcutaneously (Brody and Goldman, '41) failed to affect either the normal estrous cycle or the response of the vaginal epithelium to estrogen administration. De Venanzi and Montenegro ( '45) reported that either cod liver oil o r P-carotene administered subcutaneously to the rat modified the vaginal smear so that epithelial cells predominated. Similarly, Thorborg ( '48) noted ' F r o m a thesis submitted to