Several studies have demonstrated that enalapril causes a clinical and hemodynamic improvement in patients with congestive heart failure. Nevertheless, the drug capability of influencing left ventricular systolic and diastolic indexes has not been evaluated. In 12 patients with severe congestive heart failure (NYHA class III-IV), treated with digitalis and diuretics, we performed a baseline evaluation through a right heart catheterization, echocardiography and radionuclide ventriculography. The effects on left ventricular systolic and diastolic function indexes after the administration of enalapril 5 mg by oral route have been evaluated. After 3 months of chronic therapy with enalapril 5 mg twice daily, we performed a further evaluation through echocardiography and radionuclide ventriculography. At the acute test we observed a significant improvement of left ventricular ejection fraction (EF), left ventricular stroke index (LVSI), and peak of filling rate (PFR), with a significant reduction of pulmonary wedge pressure (PWP) and peripheral vascular resistance (PVR). After 3 months of chronic therapy EF was significantly increased with respect to baseline values (37 +/- 6.9% vs 28.7 +/- 7.9%, p less than 0.05) and showed a further increase after the drug administration (from 37 +/- 6.9% to 48 +/- 5.4%, p less than 0.001). PFR showed a similar behaviour and reached at the follow-up evaluation normal values (from 1.97 +/- 0.7 edv/s to 2.57 +/- 0.6 efv/s, p less than 0.001). Furthermore, the echocardiographic dimensions of the left ventricle decreased significantly with a significant increase of shortening fraction. In conclusion, our study demonstrates that in patients with severe congestive heart failure enalapril improves the left ventricular systolic and diastolic function indexes and this improvement is persistent.