The influence of age on six Doppler echocardiographic indices of left ventricular diastolic function was assessed in 86 normal volunteers aged from 20 to 74 years (mean 36). Five of the six indices showed a linear relation with age. Duration of isovolumic relaxation and maximal late diastolic (atrial) flow velocity increased significantly with age (r = 0.34 and r = 0.69), respectively). Conversely, maximal early diastolic flow velocity, the rate of decrease (deceleration) of flow velocity in early diastole, and the ratio between maximal early and late diastolic flow velocities decreased significantly with age (r = -0.30, r = -0.40, and r = -0.63, respectively). Duration of the early diastolic flow velocity peak did not show a linear relation with age (r = 0.04). Comparison of Doppler indices of diastolic performance among different age groups (20 to 29 years, 30 to 49 years, and 50 to 74 years) also showed an influence of aging on these diastolic variables. Isovolumic relaxation was significantly longer in older subjects than in either the intermediate or the younger age groups. In addition, both the rate of decrease of flow velocity in early diastole and the ratio between maximal early and late diastolic flow velocities were significantly reduced in older subjects. Multivariate linear regression analysis showed that after adjustment for left ventricular wall thickness and cavity dimension, percentage systolic shortening, and heart rate, age continued to correlate significantly with most Doppler indices of diastolic function. The isovolumic relaxation phase and the early and late filling phases of diastole, as assessed by Doppler echocardiography, are importantly and independently affected by aging. Hence the effects of age should be taken into account when the normal limits for Doppler indices of left ventricular diastolic function are defined.