In order to clarify the effect of age on the cardiovascular function in essential hypertension, hemodynamic studies using dye dilution method were performed in 110 uncomplicated hypertensives of ages 20 to 72 (male 71, female 39) and 94 healthy normotensives of ages 14 to 87 (male 73, female 21). In both groups, stroke volume, cardiac output and left ventricular work decreased with age, but heart rate was not correlated with age. On the other hand, total peripheral resistance increased with age. However, the difference in hemodynamic alterations between normotensive and hypertensive groups was not statistically significant. Accordingly, the effect of physiological aging on the circulatory system gradually progresses with age and the grade of progresses is almost similar in both groups. Whereas in normotensive group pulse pressure tended to decrease with age from adolescence to about 45 years and to increase thereafter, in hypertensive group pulse pressure showed high values throughout all ages, suggesting of the importance of arterial capacitance as an etiological factor of hypertension. From this study it was also suggested that the hemodynamic pattern is high flow-slightly high resistance in younger hypertensives and normal flow-high resistance in older hypertensives.