The effect of oral spironolactone (200 mg daily) on acne vulgaris has been studied in 21 women in a randomized, placebo‐controlled, double‐blind crossover study using 3 month treatment periods. Compared with placebo, spironolactone produced significant improvement as assessed by subjective benefit (P<0.001), number of inflamed lesions (P<0.001) and by an independently evaluated photographic method (P<0.02). There was a fall in sex hormone binding globulin but no significant changes in plasma testosterone and derived free testosterone. Initial plasma androgen levels were no higher in responders than in non‐responders, nor did oral contraceptive use appear to affect clinical response. Spironolactone is a useful alternative therapy for women with acne vulgaris.