Abstract
In studies of the inactivation in vivo of [alpha]-estradiol by the rat''s liver, it was found that admn. of 0.5 mg. of progesterone daily reduces the amt. inactivated. The peripheral effectiveness of the [alpha]-estradiol for vaginal cornification is decreased by the simultaneous admn. of 0.5 rag. of progesterone daily. These findings are discussed in relation to the decreased hepatic inactivation of [alpha]-estradiol produced by partial hepatectomy.