6[alpha]-Methyl-17[alpha]-acetoxyprogesterone is a highly active progestin based on its ability to promote a secretory endometrium and to prevent ovulation in rabbits. Subcutaneously, 6[alpha]-methyl-17[alpha]-acetoxyprogesterone is 6-8 times and orally 60-75 times as active as 17[alpha]-acetoxyprogesterone in the Mc Phail assay. The ability of the 6-methyl compound to inhibit ovulation in rabbits is at least 20 times as great as that of progesterone subcutaneously, while 17[alpha]-acetoxy-progesterone is 7 times as active as progesterone.