We studied 21 patients undergoing valve replacement for severe aortic stenosis and marked left ventricular dysfunction (mean ejection fraction 27 +/- 7.9%) without significant coronary disease or other valve diseases. At 5-60 months (average 26 +/- 18) after surgery, the patients underwent a clinical history, physical examination and a complete M-mode, two-dimensional and Doppler transthoracic echocardiographic study. Thirteen patients were examined with cardiopulmonary exercise testing. Two patients with a low preoperative transvalvular pressure gradient (<50 mm Hg) died postoperatively. Nineteen patients were tested at follow-up. All patients showed an improvement in functional class, an increase in ejection fraction (EF), a normalization in left ventricular diameters, volumes and stress indices and a reduction in left ventricular mass which correlated with EF increase. Cardiopulmonary exercise testing showed a good exercise capacity. In conclusion, in patients affected by severe aortic stenosis and marked preoperative left ventricular dysfunction valve replacement induces a favorable remodeling of the left ventricle, as shown by a late postoperative examination. The regression of hypertrophy is a positive event which correlates with the improvement in EF.