The history of progesterone and hormone replacement therapy goes back to 1934 when Butenandt obtained crystalline progesterone and Kaufmann started to treat ovariectomized women with both estrogens and progesterone (Table 1). Today synthetic perorally active 19-nortestosterone and 17-alpha-hydroxyprogesterone derivatives are used in addition to contraception and hormone replacement therapy in a variety of gynecological disorders. In hormone replacement therapy progestin is added only to prevent development of hyperplasia of the endometrium and its consequences. However, because progestins may cause both subjective and metabolic adverse effects minimum effective antiproliferative doses are recommended. The duration of the progestin phase cannot be shortened to less than 10 days whereas the frequency of administration apparently can be reduced without increased risk of hyperplasia. Development of new modes of administration may further help in reduction of the doses.