From June 1978 to December 1989, 158 patients over 75 years of age (mean: 78 years; range 75 to 86 years) underwent 164 valve replacements: 134 in the aortic, 18 in the mitral and 6 in double mitral and aortic positions. One hundred and seven of these valves (66%) were bioprostheses, 93 aortic and 14 mitral and 57 valves (34%) were mechanical prostheses; 47 aortic and 10 mitral. Hospital mortality (less than or equal to 30 days) was 7% (11 patients, all in NYHA class III or IV) but was higher in patients who had undergone associated procedures (9.8%; 6/61 patients) or in patients who had mitral valve replacements (11%) and in double valve replacement (16.6%). Because of a minimal delay of one year, long term follow-up information (100%) was only obtained from the first 110 patients discharged from hospital. Late mortality has been 13.6% and actuarial survival at 11 years was 71.5% +/- 5. Therefore, despite a hospital mortality of more than twice that of patients operated upon under 75 years of age (3.3%), an actuarial survival at 11 years, similar to that of patients under 75 years (77 +/- 5%) and the functional improvement obtained (95% of survivors are NYHA class I or II) certainly justify surgery in these patients. Because of the incidence of anticoagulant related hemorrhages in these patients (1.7% patient year) and since, structural deterioration of the bioprostheses was non existent in this series, a bioprosthesis appears to be the best valvular substitute in patients over 75 years of age.