Five females with idiopathic hirsutism, ten with adrenogenital syndrome, four with acne vulgaris, and three with Stein-Leventhal syndrome were treated for nine months with large or small doses of cyproterone acetate (100 or 2 mg daily, respectively) in combination with oestrogen. The drug had a good effect on the acne vulgaris and moderated the hirsutism. In the various patient groups the serum testosterone level was decreased to between 58.6% (+/- 28.7% S.E.) and 10.8% (+/- 8.2% S.E.) of the basal value. No essential difference in effectiveness was observed between the large and small doses. Based on study of the side-effects, it is recommended that laboratory liver tests are used for control.