Hyperinsulinemia or insulin resistance is suggested to play a role in the pathogenesis of hypertension and its target organ diseases. It is also well documented that aging is associated with a decline in glucose tolerance and insulin sensitivity, but there are few reports on the relationship between aging and insulin sensitivity or on the effects of aging on the progression of cardiovascular complications in patients with essential hypertension. To clarify these effects of aging in essential hypertension, 44 patients were examined by the euglycemic hyperinsulinemic glucose clamp test and ultrasonography of the heart and carotid arteries. There was a significant negative correlation between aging and insulin sensitivity (r = -0.37, p < 0.05). Significant increases in left ventricular mass index and carotid wall thickening accompanied by insulin resistance were seen in only non-elderly patients but not in elderly patients. These results suggest that aging decreases insulin sensitivity even in essential hypertensive subjects and that insulin resistance does not affect the progression of cardiac hypertrophy and atherosclerosis in elderly patients with essential hypertension.