Essential hypertension is frequently associated with several metabolic abnormalities, of which obesity, glucose intolerance, and dyslipidemia are the most common. This report discusses the epidemiologic evidence for the coexistence of these risk factors and questions why hyperinsulinemia and essential hypertension cosegregate. The euglycemic insulin clamp and the insulin suppression test are documented with respect to the physiologic functions of insulin, and the mechanisms of insulin resistance in essential hypertension are discussed. Evidence to suggest that insulin resistance is a marker for an "atherogenic syndrome" is reviewed. It is concluded that all the hemodynamic and metabolic disorders of essential hypertension and insulin resistance are closely related. The clinical approach to the patient with any of the abnormalities in question should take into consideration the whole cluster, with therapy aimed at ameliorating the entire hemodynamic-metabolic profile.