From 1974 till November, 1986, 268 adult patients aged from 15 to 84 years (11 p. cent over 70) underwent isolated aortic valve replacement by Björk-Shiley prosthesis. 81 p. cent of the prosthetic valves implanted were size 21 or over. The initial lesion was aortic stenosis (AS) in 40 p. cent, aortic regurgitation (AR) in 35 p. cent and aortic disease (AD) in 25 p. cent of the cases. The aortic valve lesions were degenerative (46 p. cent), rheumatismal (18 p. cent), congenital (12 p. cent), infective (19 p. cent including acute infective endocarditis) or dystrophic (7 p. cent) in origin. Pre-operatively, 54 p. cent of the patients were in NYHA functional class III and 14 p. cent in NYHA functional class IV. 7 p. cent presented with permanent atrial fibrillation. Mean pre-operative cardiac index was 2.49 1/mn/m2. Peri-operative mortality (up to 30 days) was 7.09 p. cent in both the 1974-79 period and the 1980-86 period; it was 3.4 p. cent in AS, 7.4 p. cent in AD and 10.7 p. cent in AR. The 249 survivors were followed up for a mean period of 5.3 years, or 1313 patient-years. 30 patients (11 p. cent) died subsequently (11 of prosthesis-related cause), giving an actuarial survival rate of 81.7 p. cent at 5 years and 71.4 p. cent at 10 years. 12 patients were reoperated upon, including 2 for prosthesis-related reasons (2.4 p. cent patient-years).(ABSTRACT TRUNCATED AT 250 WORDS)