A physiological study of the effects of menopause on vaginal function involving 14 postmenopausal women aged 51 to 70 years is reported. Initial evaluations in the estrogen-deprived state were hormonal and cytological studies, vaginal pH, quantity of vaginal fluid, transvaginal electropotential difference, and vaginal blood flow. A significant fall in vaginal pH and increases in transvaginal potential difference, the quantity of vaginal fluid, and vaginal blood flow were observed after estrogen replacement therapy. The results before and after treatment are compared with norms established for women younger than 40 years.