The effect of spironolactone on female hirsutism was studied in 18 patients. The drug was administered at the dose of 400 mg for the first ten days and 300-200 mg later on in a first group of women (Group A); a second group (Group B) was given 200 mg spironolactone for the whole length of therapy. A significant decrease of the index of Ferriman and Gallwey (p = 0.01) was noted from the 100th day of treatment; acne and seborrhoea improved concomitantly. Plasma total testosterone values fell from 0.64 +/- 0.24 ng/ml to 0.32 +/- 0.12 ng/ml (p = 0.002) during the first 5 days only in the patients of Group A; in the other patients no significant changes were observed. PRL did not significantly change from pretreatment values; FSH and LH values at the 5th, 10th, and 15th day of therapy did not show a uniform course in both groups. On the basis of these results spironolactone administration appears promising in the therapy of female hirsutism.