Insulin-sensitizing agents have been recently proposed as the therapy of choice for polycystic ovary syndrome (PCOS), since insulin resistance and associated hyperinsulinemia are recognized as important pathogenetic factors of the syndrome. Moreover, since almost all obese PCOS women and more than half of those of normal weight are insulin resistant, and therefore present some degree of hyperinsulinemia, the use of insulin sensitizers should be suggested in most patients with PCOS. Insulin sensitizer treatment has been associated with a reduction in serum androgen levels and gonadotropins, and with an improvement in serum lipids and in prothrombotic factor plasminogen-activator inhibitor type 1, whatever the insulin sensitizer used. This therapy has also been associated with a decrease in hirsutism and acne, and with a regulation of menses and an improvement of ovulation and fertility. Notable improvements in all these parameters have also been described after a change in lifestyle approach, particularly in the presence of obesity. Lifestyle interventions should therefore be combined with insulin sensitizers in PCOS when obesity is present.