Polycystic ovarian syndrome (PCOS) is extremely common among reproductive-aged women, but often goes undiagnosed. PCOS is associated with the metabolic syndrome and carries a greatly increased risk of impaired glucose tolerance and type 2 diabetes mellitus, and cardiovascular risks. Treatment of PCOS may provide relief of cosmetic problems and depression by improving patient self-esteem. In addition, because of its association with the metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease, its recognition and treatment can potentially be life saving. This article reviews the impact, pathophysiology, and associated risks of obesity and the metabolic syndrome in PCOS.