The long-term results and the prognostic factors in aortic valve replacement for aortic stenosis were assessed from a series of 249 operated cases (comprising 199 pure or dominant stenosis and 50 mixed aortic lesions) followed up for a maximal period of 9 years. The postoperative survival rate, 71% at 5 years, 62,6% at 8 years, including the operative mortality, is better than in a comparable series of pure chronic aortic incompetence (58% at 5 years) despite a higher average age. In the same age group the difference is significant at the 6th year. However, no difference was observed between mixed aortic disease and aortic stenosis. Irreversible myocardial dysfunction is relatively rare (6,6% of survivors at 1 month, 24% of poor results or late deaths) and much less common than in aortic incompetence of which it represents the main cause of failure. Even in these cases, prolonged symptomatic improvement may be observed. 3 prognostic factors affect the operative and late mortality. They act to variable degrees and independantly of each other. They are : age, cardiomegaly and heart failure. The actuarial 5 year survival is: 81,77% and 53% for under 50, 50 to 65 and over 65 years age group respectively; 88%, 78% and 48% for cardiothoracic ratios of less than 0,50, between 0,50 and 0,58 and greater than 0,58 respectively; 83%, 65% and 47% for patients without signs of heart failure, with a history of pulmonary oedema, and with a history of congestive cardiac failure respectively. These results encourage a liberal attitude towards surgery, even in old patients with severe valvular lesions.