This study was performed to confirm the therapeutic effects of low-dose (2.5 mg/day) finasteride in hirsute women. Our study was a non-randomized prospective clinical trial. Twenty-nine patients with hirsutism were included in the study. The patients received 2.5 mg finasteride once a day over a period of 12 months. Follicle stimulating hormone, luteinizing hormone, sex hormone binding globulin, 17alpha-hydroxyprogesterone, estradiol, androstenedione, total and free testosterone, dehydroepiandrosterone sulfate levels and hirsutism scores were determined in all patients before treatment and at every 6 months during the therapy. The hirsutism score decreased from a mean of 18.4 +/- 4.6 to 8.4 +/- 4.2 during the study. The per cent reduction in hirsutism score (mean +/- SD) at 6 and 12 months was 29.2 +/- 14.5 and 55.7 +/- 14.9%, respectively. There were no significant differences in any of the hormone levels and no serious side-effects were observed during the treatment. In conclusion, low-dose finasteride (2.5 mg/day) is a cost-effective, well-tolerated therapeutic agent without significant abnormal biochemical findings and can be used in place of high-dose (5 mg/day) finasteride in the treatment of hirsutism.