From March 1977 to December 1981, 872 patients at our institution underwent valve replacement with a pyrolytic carbon tilting disc prosthesis manufactured in Italy by SORIN-Biomedica. To verify the performance characteristics of this prosthesis, we analyzed the intermediate-term results obtained over a cumulative total of 3,041 patient-years (pt-yr) of follow-up. Three hundred sixty-nine patients underwent mitral valve replacement (MVR), 309 had aortic valve replacement (AVR), and 194 had both mitral and aortic (double) valve replacement (DVR). Expressed in actuarial terms (% [+/- standard error of the mean] free of adverse events at 5 years) and in linearized terms (% pt-yr), respectively, valve-related complications occurred at the following rates: Thromboembolism, 89.9 +/- 1.9% and 2.1 +/- 0.4% pt-yr (MVR); 92.1 +/- 1.9% and 1.7 +/- 0.4% (AVR); 90.5 +/- 5.0% and 2.2 +/- 0.6% (DVR). Anticoagulant-related hemorrhage, 95.2 +/- 1.5% and 1.4 +/- 0.3% (MVR); 95.9 +/- 1.5% and 1.3 +/- 0.3% (AVR); 96.0 +/- 2.0% and 0.9 +/- 0.4% (DVR). Prosthetic valve endocarditis, 99.0 +/- 0.6% and 0.2 +/- 0.1% (MVR); 97.4 +/- 1.0% and 0.6 +/- 0.2% (AVR); 94.5 +/- 1.7% and 1.4 +/- 0.4% (DVR). Reoperation, 92.6 +/- 1.5% and 1.7 +/- 0.3% (MVR); 89.4 +/- 1.9% and 2.4 +/- 0.4% (AVR); 82.3 +/- 2.9% and 4.8 +/- 0.8% (DVR). The total valve-related morbidity and mortality was 79.6 +/- 2.6% and 4.9 +/- 0.6% (MVR); 79.7 +/- 2.6% and 5.1 +/- 0.6% (AVR); 70.5 +/- 4.0% and 7.7 +/- 1.1% (DVR). The 5-year actuarial survival rate without hospital mortality was 86.8 +/- 2.0% (MVR), 91.0 +/- 1.7% (AVR), and 78.8 +/- 3.7% (DVR). The intermediate-term survival and complication rates showed the performance of the SORIN prosthesis to be quite satisfactory.