The aim of this study was to evaluate (1) the effect of endurance training on left ventricular and right ventricular diastolic function and (2) whether the normal aging effect on left ventricular and right ventricular diastolic function is slowed by endurance training. A total of 269 healthy subjects were prospectively enrolled for echocardiographic evaluation. Five groups were defined on the basis of age and athletic activities: (1) young (18 to 39 years) nonathletes (n = 62), (2) veteran (>or=40 years) nonathletes (n = 33), (3) young regular athletes (9 to 18 hours of sports/week; n = 58), (4) young elite athletes (>18 hours of sports/week; n = 63), and (5) veteran athletes (>or=40 years and >or=9 hours of sports/week; n = 53). Pulsed-wave Doppler indexes for diastolic function in the left and right ventricles were obtained at rest. No significant differences were found among the young controls, regular athletes, and elite athletes in left ventricular and right ventricular pulsed-wave and tissue Doppler diastolic parameters. These were also comparable between the veteran athletes and controls. In athletes and controls, similar and significant correlations were found between age and diastolic parameters. Age was the most important determinant in almost all parameters in multivariate analysis, while the influence of the amount of training did not account for >2% of the observed variance in any of these parameters. In conclusion, the amount of endurance training did not alter diastolic parameters in either ventricle in the young. Furthermore, the biventricular decreases in diastolic function observed in healthy, nonathletic subjects with age was also observed in aging athletes' hearts.