Six hundred and nineteen consecutive patients had aortic valve replacement between January 1983 and January 1993 with the zero pressure fixed Biocor porcine bioprosthesis. Mean age was 66.2 years (range 17-88 years). Male/female ratio was 416/203. Concomitant cardiac procedures, mainly coronary bypass surgery, were performed in 35% (214/619). Early mortality was 5.9% (37/619). Late mortality was 15.8% (92/582). Actuarial survival at 10 years was 60.0 +/- 4.9% and freedom from valve-related mortality was 97.6 +/- 0.8%. Total follow up was 2308 years. The follow up was 99.2% complete. Thromboembolic rate was 1.1%/pty (fatal 0.1%/pty, major 0.3%/pty and minor 0.6%/pty). The incidence of prosthetic valve endocarditis was 0.3%/pty (fatal 0.1%/pty). Freedom from reoperation due to structural valve deterioration, non-structural dysfunction and prosthetic valve endocarditis was 78.1 +/- 10.7%, 98.5 +/- 0.6% and 97.6 +/- 0.9%, respectively. The occurrence of structural valve deterioration varied considerably between age groups. In patients below 50 years of age the actuarial freedom from structural valve deterioration was 52.4 +/- 22.0%, while it was 96.2 +/- 1.1% for those between 71 and 80 years. At the 10-year follow up all patients had improved clinically. Preoperatively, 75% of the patients were in NYHA classes III or IV compared to 8% at the 10-year follow up. We conclude, that the Biocor bioprosthesis has a low rate of complications in terms of thromboembolism, anticoagulant-related bleeding, prosthetic valve endocarditis and valve-related mortality as compared to mechanical valves and also to other bioprostheses. The durability of the Biocor bioprosthesis has increased slightly compared to that reported with other, earlier models when inserted in patients above 50 years of age.