Bilateral adrenalectomy resulted in a greater sensitivity of the vagina of the castrated rat to continuous stimulation by estradiol benozate. De-soxycorticosterone acetate (DCA) and progesterone decreased the vaginal sensitivity of castrated rats to continuous stimulation by estradiol benzoate. DCA and progesterone neutralized the effect of adrenalectomy on the sensitivity of the vagina to estradiol in castrated rats. Hypophysectomy, within 20 days postoperatively, did not alter the vaginal sensitivity to estradiol in castrated rats.