Nineteen patients, aged 58-80 years, with severe isolated aortic valve stenosis, severely reduced ejection fraction and clinical heart failure underwent aortic valve replacement between January 1970 and April 1977. Ten had concomitant coronary artery disease (all underwent additional coronary bypass surgery), 17 had angina pectoris and four had syncope. Aortic valve area index was 0.32 +/- 0.03 cm2/m2 (mean +/- SEM); left ventricular (LV) end-diastolic volume index was 117 +/- 9 ml/m2 and LV ejection fraction was 0.37 +/- 0.02. There were four operative deaths and one late death. The follow-up time ranged from six to 74 months (38 +/- 6 months). Actuarially determined three-year survival is 74 +/- 10%; the expected five-year survival is the same. One patient had a serious cerebrovascular accident. Of the remaining survivors, seven were initially Functional Class IV and six Class III; currently, six are Class I and seven Class II (New York Heart Association classifications). The cardiothoracic ratio has decreased from 0.54 +/- 0.03 to 0.49 +/- 0.03. Repeat hemodynamic evaluation has been performed in 10 patients, 22 +/- 6 months after surgery. In these 10 patients, the aortic valve gradient decreased from 55 +/- 7 11 +/- 1.3 mm Hg; LV end-diastolic pressure from 22 +/- 2.4 to 9 +/- 1.9 mm Hg; LV end-diastolic volume index from 119 +/- 16 ml/m2 to 107 +/- 11 ml/m2. LV ejection fraction has increased dramatically from 0.34 +/- 0.03 to 0.63 +/- 0.05 and mean velocity of circumferential fiber shortening from 0.57 +/- 0.08 to 1.3 +/- 0.18 circ/sec. The encouraging long-term survival, improved functional class and the marked improvement in left ventricular function that occurred in our patients indicate that all patients with severe aortic stenosis in clinical heart failure should be offered aortic valve replacement.