While the incidence of essential hypertension is not increased in type 1 diabetics, it is about three times as high in type 2 diabetics. Since in 50% of the cases, hypertension is present before the metabolic disorder becomes manifest, an association between the etiologies of the two disturbances was suspected as long as 65 years ago. A new understanding of the significance of insulin resistance and hyperinsulinemia suggests that the two conditions are part of a single metabolic disorder. This is supported by the fact that normal-weight hypertensives can also manifest insulin resistance, and they more often develop a type 2 diabetes mellitus. These facts urge us to re-think our therapeutic approach to hypertension, and to employ, as far as possible, only those substances that have no negative influence on the incidence of the metabolic disorder. With the introduction of ACE-inhibitors capable of improving insulin sensitivity, we now have, for the first time, the possibility of improving the prognosis of the metabolic syndrome. Moreover, their molecular mechanism of action provides initial clues as to the possible etiology of the syndrome.