The authors of this article have been trying to find out how natural progesterone contained in Utrogestan tablets are absorbed by the body when these tablets are placed in the vagina. To do this they conducted their studies on genitally active young women who had volunteered, who were not pregnant and who were not taking hormones. Several therapeutic protocols were tested. Vaginal administration of 100 mg of progesterone (1 Utrogestan tablet) resulted in an increase in blood progesterone levels within an hour. It reached its maximum level after 2 to 6 hours and lasted for 24 hours on an average. The average level was 3.7 ng/ml with a dose of 100 mg/day and 9.7 ng/ml with a dose of 200 mg/day. One capsule every 12 hours ensures that the least variation between individuals occurs. It is the most worth-while dosage and the one recommended by the authors of this article.