In a consecutive series of thirty-six male and female patients referred with severe acne, the effect of 3 months' treatment with placebo or spironolactone (50-200 mg daily) on sebum excretion and clinical and endocrine status was evaluated double-blind. Twenty-six patients completed the study. Abnormal free androgen indices were found in 27% of the original nineteen female subjects. Spironolactone reduced sebum excretion in all female subjects, but there was no correlation between sebum response and androgen status. The clinical response was dose-dependent, with maximum subjective and objective benefit when spironolactone doses of 150-200 mg were used.