The goal of this article is to differentiate the insulin resistance syndrome from the metabolic syndrome. In the case of the insulin resistance syndrome, the abnormalities and clinical syndromes that are increased in prevalence in insulin-resistant individuals have been summarized, with a brief discussion of the causal relationship between insulin resistance, compensatory hyperinsulinemia, and associated consequences. Discussion of the metabolic syndrome has focused on the five criteria chosen by the adult treatment panel III to diagnose the syndrome, evaluating them in terms of their relationship to insulin resistance and their role as cardiovascular disease risk factors.