The association with polycystic ovary syndrome must be investigated in all cases of anovulatory menstrual disturbances. A significant number of the cases exhibit hyperinsulinemia determined by hyporesponse of the target cells to insulin. The treatment of the hyperinsulinemic patients with metformin or its analogues increases the sensibility to insulin and reduces the hyperinsulinemia. The treatment is associated with the decrease of androgen levels and the menstrual and ovulatory regulation in most cases, and increases the rate of spontaneous or induced pregnancy. The occurrence of adverse events is minimal.