Between January 1971 and December 1978, 865 standard Björk-Shiley prostheses (spheric or conic carbon disc) were implanted in the Department of Thoracic and Cardiovascular Surgery of the University Hospital of Rennes. Three hundred and fifty seven consecutive patients who underwent isolated aortic valve replacement were included in the study : 246 men (69%) and 111 women (31%) with an average age of 57.5 years (range : 24-80 years). One hundred and sixty eight patients (48%) were in NYHA Class II. 141 (39%) in Class III and 48 (13%) in Class IV. The valvular disease was stenotic in 304 cases (85%) and regurgitant in 53 cases (15%). The hospital mortality was 35 (9.8%). The main causes of death were cardiac (23 cases, 66%). The long-term results contain 322 survivors of surgery (mean follow-up 12 years, follow-up rate 99%, representing 3726 patient-years). The actuarial survival (including hospital mortality) was 76% at 5 years. 61% at 10 years, 47% at 15 years and 26% at 20 years. The average age of the survivors at present is 71 years and 95% are NYHA classes I or II. The causes of the 171 late fatalities were cardiac in 49 cases (1.3% per patient-year). Death was related to the prosthesis in 32 cases (0.8% per patient-year) : 3 endocarditis, 17 bleeding complications, 12 systemic emboli. Deaths were extracardiac in 58 cases (1.5% per patient-year). Prosthesis-related complications were : 9 paravalvular leaks (0.2% per patient-year), 3 dysfunctions (0.1% per patient-year). 24 haemorrhages (0.6% per patient-year), 5 thromboembolic episodes (0.1% per patient-year). 5 endocarditis (0.1% per patient-year). No structural abnormalities of the prostheses were observed. The authors confirm the reliability of the standard Björk-Shiley valve prosthesis in the aortic position and the value of the aortic valve replacement by a mechanical prosthesis even at very long term.