Cyproterone acetate given as a single intramuscular dose of 300 mg monthly for 6 months resulted in significant reduction of hirsutism without appreciable side effects. This regimen resulted in decreased levels of luteinizing hormone (LH) and estradiol in the eight women studied. No significant changes were observed in total serum testosterone (T) levels, however, there was a reduction in sex hormone binding globulin (SHBG), resulting in lowered SHBG-bound T, and an increase in non-SHBG-T over this time. Serum androstanediol glucuronide levels decreased in three of four women, although not to normal levels.