II alpha-Hydroxyprogesterone, a synthetic antiandrogen of low toxicity, was applied topically. In short-term experiments the sebum production of the forehead in normal male subjects was reduced significantly. The cholesterol concentration of sebum decreased to a greater extent. In long-term studies in patients with seborrhoea and male-pattern alopecia, the steroid caused a marked and constant reduction of greasiness of the hair. In this group also, the cholesterol concentration of the sebum obtained from scalp hair decreased more markedly than total sebum production. Possible effects of II alpha-hydroxyprogesterone on androgenic alopecia are discussed.