The aim of our study was to determine whether exercise training can augment left ventricular diastolic filling at rest and during exercise in patients with ischemic cardiomyopathy and whether any correlation exists between changes in diastolic filling and changes in exercise tolerance. Forty-three consecutive patients (mean age, 54 +/- 8 years) with ischemic cardiomyopathy and severe left ventricular systolic dysfunction (election fraction <30%) were studied. Group T (29 patients) was exercised on a cycle ergometer 3 times a week for 8 weeks at 60% of peak oxygen uptake. Group C (14 patients) was not exercised. All patients underwent an exercise test and a radionuclide ventriculography at baseline and after 8 weeks. At the end, no changes were found in group C. In group T, exercise training increased peak oxygen uptake (1 5%; p < 0.0001), work rate (1 5%; p < 0.005), peak early filling rate (10%; p < 0.02), and peak filling rate (1 1%; p < 0.03). At submaximal exercise, peak filling rate increased at all matched heart rates. The increase in peak filling rate was correlated with the increase in cardiac index (r= 0.72; p < 0.0001) at peak exercise. The independent predictors of the increase in peak oxygen uptake were changes in work capacity and peak early filling rate. The data demonstrate that exercise training can improve the exercise capacity of patients with ischemic cardiomyopathy and severe systolic-dysfunction. The increase in early diastolic filling at rest and during exercise may contribute to the improvement in peak oxygen uptake.