OBJECTIVE: To compare the clinical efficacy and safety of the combination of spironolactone (100 mg/day) plus finasteride (5 mg/day) and spironolactone (100 mg/day) alone in the treatment of hirsutism. PATIENTS AND MEASUREMENTS: Sixty-five hirsute women were randomly assigned to one of these two treatment groups. Hirsutism score was measured according to the modified Ferriman-Gallwey scoring system. Baseline and post-treatment assessments were carried out in each subject by an investigator blinded to the therapy. Both groups had similar demographic properties at baseline. The serum levels of total and free testosterone, dehydroepiandrosterone sulphate and sex hormone-binding globulin were measured at the beginning and after 1 year of therapy. Blood chemistry and side-effects were evaluated during the study. Hirsutism scores were decreased significantly in both groups at the end of the year. RESULTS: The mean percentage change in hirsutism scores from baseline in the spironolactone plus finasteride-treated group (51.3%) was significantly (P<0.005) higher than in the group treated with spironolactone alone (36.6%). Patients from both treatment groups experienced similar side-effects. CONCLUSIONS: We have concluded that a combination of spironolactone plus finasteride is a safe and effective therapy in the treatment of hirsutism.