OBJECTIVE To elucidate the role of hypertension as part of a state of insulin resistance. METHODS Thirty-one uncomplicated hypertensive men not receiving antihypertensive treatment or who had been without treatment for a 4-week washout period and 10 lean normotensive controls were compared. Hypertensive men were divided according to their body mass index into three groups. All subjects came to the clinic for measurements of height, weight, hip and waist circumferences, and sitting blood pressure, and to begin 24 h ambulatory blood pressure monitoring. Plasma glucose and insulin levels were measured during a 2 h oral glucose (75 g)-tolerance test. For the hypertensive population as a whole, behaviors of studied variables among dippers (n = 18) and nondippers (n = 13) were determined. RESULTS During oral glucose-tolerance testing blood glucose levels after 60 min and 120 min were significantly higher (P < 0.05) in members of the high body mass index group than they were in members of the low body mass index group. Insulin levels of members of the high and middle body mass index groups were higher than those of members of the low body mass index group after 60 min (P < 0.05 for both comparisons) and 120 min (P < 0.05 for both comparisons). The mean serum insulin level in members of the low body mass index group was significantly higher than that in normotensives after 30 min, 60 min and 120 min (P < 0.05 for all three comparisons). The mean serum insulin: plasma glucose ratio for men in the low BMI group was significantly higher than that for normotensives after 60 min and 120 min (P < 0.05 for both comparisons). Correlations of blood pressure and insulin levels were not significant. Levels of high-density lipoprotein cholesterol and triglycerides were lower in members of the group with high body mass index than they were in members of the group with low body mass index. Total cholesterol: high-density lipoprotein cholesterol ratio was higher for members of the high body mass index group than it was for members of the middle body mass index group. Weight, body mass index, casual systolic blood pressure, 24 h average systolic blood pressure and diastolic blood pressure, 0700-2300 h systolic blood pressure, and 24 h average heart rate-systolic blood pressure product of dippers were significantly lower than those of nondippers. CONCLUSIONS These results suggest that hypertension and being overweight have additive effects increasing insulinemia and that being overweight is associated with a significantly lower nocturnal fall in blood pressure.