We measured systemic hemodynamic, volume, and endocrine findings in 100 hypertensive women matched to 100 men by mean arterial pressure, age, race, and body surface area. Women had a higher resting heart rate, cardiac index, and pulse pressure and lower total peripheral resistance (all p less than 0.01) than men with the same pressure level. Isometric stress caused an increase in arterial pressure that was almost 50% higher in men than in women. The sexual difference in cardiovascular findings was significant before but not after menopause. For any level of arterial pressure, total peripheral resistance (and therefore the risk of hypertensive cardiovascular disease) was lower in women than in men. We conclude that premenopausal women are hemodynamically younger than men of the same chronologic age. Our study identifies a pathophysiologic mechanism for the clinical and epidemiologic finding that essential hypertension is less lethal in women than in men.