Type 2 diabetes and lesser degrees of glucose intolerance are associated with insulin resistance, central obesity, hypertension, and dyslipidaemia. The term metabolic syndrome describes the same constellation, with or without glucose intolerance. Although these associations are well established, their pathophysiological basis remains unclear, and no unifying feature has emerged. Attempts have been made to assemble the various features of the metabolic syndrome into a single all-purpose definition, for which diagnostic, prognostic, and therapeutic value has been claimed. Diagnosis of the metabolic syndrome is redundant in those who already have diabetes and adds nothing to the management of those who do not.