The polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age. It is characterised by hyperandrogenism and menstrual disturbances. Affected women suffer from hirsutism, alopecia and acne. Anecdotal improvement of acne by treatment with insulin-sensitizers has been reported but a systematic evaluation has not yet been performed. We evaluated the influence of metformin on the degree of acne papulopustulosa in PCOS women.