Background: Spironolactone has an anti androgenic effect, inhibiting the binding of androgens to their receptor. This antagonistic effect is the basis for the use of spironolactone in the treatment of hirsutism. Aim: To study the effectiveness and safety of spironolactone in the treatment of hirsute women and of the association of spironolactone plus dexamethasone in the treatment of hirsutism with glucocorticoid sensitive hyperandrogenism. Patients and method: Sixteen women (group 1) with peripheral hirsutism (defined as those with normal androgens levels, normal menstrual cycles and ovulation) and 24 women (group 2) with glucocorticoid sensitive hyperandrogenic hirsutism were studied. Group 1 was treated with spironolactone 50 mg bid and group 2 with same spironolactone dose plus dexamethasone 0.5 mg at 23 h during one month and 0.25 mg thereafter. Patients were followed during one year. Results: After one year of treatment, a 54% reduction in Moncada hirsutism escore was observed in group 1 and 52% reduction in group 2. Observed secondary effects of spironolactone were increases in diuresis, fatigability, acne aggravation and seborrhea in two patients. Two additional patients had spotting. No secondary effect attributable to glucocorticoid use were observed. Conclusions: Spironolactone is effective and safe in the treatment of hirsutism. Androgenic supression did no increases its effectiveness, underscoring the peripheral anti androgenic activity os spironolactone. (Rev Méd Chile 2000; 128: 868-75).