A group of 41-year-old hypertensive men (n = 35, blood pressure (BP) 149.9 +/- 2.1/98.9 +/- 1.1 mmHg, mean +/- SEM) who had never received treatment for their condition were compared with hypertensive women of the same age (n = 18, BP 155.9 +/- 4.3/98.1 +/- 1.6 mmHg) with comparable body mass index (BMI, 25.9 +/- 0.5 vs. 24.9 +/- 4.5 kg m-2) who, also, had never received treatment. The lipid profile was more atherogenic in the men, with lower HDL cholesterol (1.21 +/- 0.04 vs. 1.38 +/- 0.06 mmol l-1, P = 0.04), higher total cholesterol (6.04 +/- 0.14 vs. 5.54 +/- 0.18 mmol l-1, P = 0.04) and triglycerides (1.80 +/- 0.16 vs. 0.96 +/- 0.10 mmol l-1, P < 0.001). The hypertensive men had higher haemoglobin (P < 0.001) and haematocrit. Plasma catecholamines were inversely related to BMI in the women only (r = -0.52, P < 0.05 for both noradrenaline and adrenaline). Women with BMI above 25 kg m-2 had significantly lower arterial plasma adrenaline and noradrenaline than those with BMI below 25 kg m-2 (28 +/- 5 vs. 78 +/- 16 pg ml-1, P < 0.01 and 101 +/- 17 vs. 206 +/- 33 pg ml-1, P < 0.01 respectively). A negative curvilinear relationship appeared between arterial adrenaline and insulin (r = 0.49, P = 0.05). These results suggest a male propensity for athero-thrombogenic risk factors in otherwise comparable hypertensive subjects. A close relationship between metabolic risk factors within the normal range seems to exist even in hypertensive women. The decreased sympathetic activity at rest in the obese hypertensive women indicates different pathophysiological mechanism for hypertension in lean and obese. Decreased sympathetic activity and thus reduced energy expenditure, promotes a risk for weight gain, and could explain the inverse relationship between insulin and adrenaline.