Obesity is one component of a risk factor constellation that consists of insulin resistance (and/or hyperinsulinemia), hypertension, and a dyslipidemia characterized by a low HDL cholesterol level and high triglyceride levels. This risk factor constellation, which conveys enhanced risk for cardiovascular disease, is sometimes referred to as the "insulin resistance syndrome", "syndrome x", or the "metabolic" syndrome. Although the hyperinsulinemia and insulin resistance associated with the syndrome appear to play a central role, the relationship between insulin and the other manifestations of the syndrome have remained obscure. (Hypertens Res 1996; 19 Suppl. I: S51-S55)