A series of 12 consecutive patients who underwent aortic valve replacement (AVR) for aortic stenosis complicated by severe left ventricular dysfunction was reviewed. Ventricular dysfunction was reflected by pulmonary congestion, edema, renal and hepatic dysfunction, and by severely depressed ejection fractions (mean, 13%; range equal to 0-20%). Aortic valve replacement was accompanied by mitral commissurotomy in 1 patient and aortocoronary bypass in 5. Three of 5 patients with greater than 50% coronary obstruction died without reversal of heart failure, and 1 of the 5 died after a stroke. The 1 survivor of this group has done well. All 7 patients with minimal or no coronary disease survived operation and are now in New York Heart Association Class I or II. Postoperative catheterization (2 to 12 months) in 6 patients showed improved cardiac index and filling pressures. Left ventricular diastolic volume fell from 159 to 82 ml/m2, and ejection fraction rose from 13 to 45%. We conclude that left ventricular dysfunction owing to aortic stenosis alone is reversible and that AVR results in great clinical improvement. When coronary disease is present, survival may be accompanied by great improvement but the operative mortality is much higher.