In the present study a parenteral treatment regimen with cyproterone acetate was compared with the high dose peroral administration in patients with severe hirsutism. Two groups consisting of 10 patients each performed treatment with either 100 mg cyproterone acetate perorally for the first 10 days of the menstrual cycle or received a monthly implant of 300 mg cyproterone acetate intramuscularly applied on the first day of each cycle. In addition, contraception was performed with Diane in both patient groups. 9 treatment cycles were followed by a posttreatment period of 3 months. Hair parameters and serum androgens were monitored regularly. No significant differences of testosterone, androstenedione, dehydroepiandrosterone-sulfate and prolactin serum levels became evident between both cyproterone acetate regimens. Measurements of facial hair diameters revealed a better reduction for the parenteral application. Also the improvement of dermatological parameters was more prominent in the parenteral treatment group. The good effects of a medium dose parenteral application against higher dose peroral treatment thus was documented. The lack of significant differences of androgenic suppression in both regimens turns up the question if different metabolism at the cellular level may be responsible for that phenomenon.