Echocardiographic and hemodynamic studies were obtained in 16 consecutive adult patients who underwent aortic valve replacement (AVR) with St. Jude Medical valve for aortic stenosis (AS). Three cases of congenital AS was included and two of them had undergone aortic valvotomy in childhood. One of 16 patients died due to late cardiac tamponade six weeks after AVR. Postoperative studies showed improved left ventricular (LV) functions. LV end diastolic and end systolic diameter (LVDs and LVDs) fell from 50.3 and 38.2 to 44.6 and 31.6 mm respectively (p less than 0.05). Fractional shortening (%FS) rose from 26.5 to 32.2% (p less than 0.05). End systolic wall stress (ESWS) fell from 126.2 to 69.6 k dynes/cm2 (p less than 0.01). Cardiac index and pulmonary arterial wedge pressure improved from 3.4 and 14.4 to 3.6 l/min/m2 and 10.5 mmHg respectively (ns). Preoperatively, six were functional class II, eight were class III and one was class IV (New York Heart Association classification). Postoperative improvement was as follows, eight: class I, seven: class II. In four cases, preoperative echocardiography revealed most depressed LV function in %FS (smaller than 21%) and ESWS (greater than 140). Postoperatively they improved from 18.3 and 164 to 26.0% and 72.8 k dynes/cm2 respectively. These results suggested that depressed LV function in the patients with longstanding AS was largely related to limited preload reserve due to LV enlargement and mechanical unloading of LV (correction of afterload mismatch) resulted in improvement of LV function. In conclusion, LV dysfunction owing to AS alone is reversible and AVR results in great clinical improvement.