Our information on the hemodynamics of the aging cardiovascular system in normotensive and hypertensive subjects is mainly based on cross-sectional studies. In normotensive subjects with no indication of coronary heart disease, recent noninvasive studies seem to indicate that cardiac output at rest and during exercise does not decline with age. These results contrast with what has been found by invasive studies in unselected populations. In hypertensive subjects it is well established that the hemodynamics of young subjects at the early stage differ greatly from what is seen in elderly hypertensive subjects. In the early phase, a high resting cardiac output is typical, whereas in the elderly, cardiac output is very low and total peripheral resistance (TPR) very high. Echo studies have shown that left ventricular hypertrophy develops early in hypertension--together with increased stiffness and reduced left ventricular compliance. A subnormal stroke volume during exercise is seen early in the process of hypertension. Data from the 20-year follow-up study of the Bergen population demonstrate that in groups of young (17-29 years) versus elderly (60-69 years) patients with hypertension with the same mean arterial blood pressure, the hemodynamic mechanisms behind increased blood pressure were widely different. The increase in mean arterial blood pressure during exercise was much steeper in the older subjects than in the younger ones, and TPR was about twice as high during 150 W exercise. Cardiac index (CI) in the oldest group was approximately half of that in the youngest group. The differing hemodynamic patterns in the young and elderly might have implications for when and how to start drug treatment, and also for what type of treatment to select.