THIS study was undertaken for the purpose of comparing the relative merits of oral and vaginal epithelial smears in an attempt to simplify or supplement the clinical method of appraising the endocrine changes during the ovarian cycle in women. Vaginal smears have been shown to be useful in studying the menstrual cycle, and it was felt that similar changes might be reflected in the oral mucosa since the latter possesses certain features in common with the vaginal mucosa, when examined histologically. For example, both areas may simultaneously present signs of leukoplakia, lichen planus, ulcers, and other diseases. On the other hand, there are differences. The oral mucosa is composed of more layers of cells than the resting vaginal mucosa; the outer basal cell layer and the intermediate and superficial cell layers of the vagina do not have exact counterparts in the oral epithelium; the cornified cells, when present, comprise the most superficial layer in the oral epithelium while in the vaginal epithelium t...