La Marca A1, Artensio AC, Stabile G, Volpe A. Abstract Insulin resistance is a common feature of PCOS. Hyperinsulinemia has been causally linked with all features of the syndrome, such as hyperandrogenism, reproductive disorders, and metabolic disturbances. Several insulin-sensitizing agents have been tested in the management of PCOS. Metformin is the only drug currently in widespread clinical use for PCOS. In a high percentage of patients, treatment with metformin is followed by regularization of the menstrual cycle, less pronounced hyperandrogenism and cardiovascular risk factors, and some improvement in the response to therapies aimed at induction of ovulation. In adolescent girls who are anovulatory and moderately obese, metformin administration can have a normalizing effect on multiple aberrations within the endocrine-metabolic status. During the reproductive period, metformin administration can improve reproductive function and the establishment of pregnancy. A role of metformin in prevention of gestational diabetes and hypertensive complications of pregnancy has yet to be shown. Finally, any real benefit of insulin-lowering treatment in terms of lesser cardiovascular risk in women with PCOS women remains to be demonstrated.