Epidemiologic and clinical studies have shown a close association between hypertension, hyperlipidemia and glucose intolerance. A metabolic imbalance has been proposed. As both hyperinsulinemia and insulin resistance appear to be of pathogenetic importance in this metabolic syndrome, we studied these features in hypertensive and normotensive subjects.Glucose disposal under a hyperinsulinemic clamp was measured and different indices of hyperinsulinemia were obtained with the intravenous glucose tolerance test. The results were evaluated in relation to different cardiovascular risk factors assessed in 194 adult subjects selected from a health screening.Both hyperinsulinemia and the glucose disposal (clamped) value were significantly correlated with blood pressure (r = 0.36 and -0.42, respectively; both P < 0.0001), free fatty acids (r = 0.20 and -0.29, respectively; both P < 0.0005), serum triglycerides (r = 0.33 and -0.39, respectively; both P < 0.0001), high-density lipoprotein (HDL) cholesterol (r = -0.31 and 0.41, respectively; both P < 0.001) and fasting glucose (r = 0.45 and -0.44, respectively; both P < 0.0001). Multiple regression analysis with age, sex and obesity as confounding variables showed that insulin resistance was superior to hyperinsulinemia in the relationships with blood pressure and indices of hyperlipidemia (elevated free fatty acids, serum triglycerides and low HDL cholesterol), but both insulin sensitivity and hyperinsulinemia were significantly related to fasting glucose.Insulin sensitivity was more closely related to blood pressure, serum triglycerides and HDL cholesterol than hyperinsulinemia, but both insulin sensitivity and the insulin levels were associated with fasting glucose. Thus, insulin resistance is more important than hyperinsulinemia as a determinant of the constellation of cardiovascular risk factors comprising hypertension, glucose intolerance and hyperlipidemia.