Polycystic Ovary Syndrome (PCOS) is the major cause of infertility in the United States. Many women with PCOS demonstrate insulin resistance and a compensatory hyperinsulinemia.This is due to both an intrinsic form of insulin resistance unique to PCOS and, in many cases, acquired insulin resistance due to obesity. The importance of this observation lies in the fact that hyperinsulinemia appears to play an important pathogenetic role in the hyperandrogenism and anovulation of both obese and lean women with PCOS.