In a prospective study, 292 consecutive patients received 336 Omnicarbon cardiac valves from September 1984 through September 1992 at the Montpellier University Hospital. There were 153 aortic (52%), 95 mitral (33%) and 44 double (15%) mitral and aortic replacements. Mean age was 58 years; 57% were male. Total follow up was 1,383 patient-years, with a maximum of nine and a mean of 4.87 years. Early mortality was 2.75% overall. Late mortality occurred at a rate of 1.9%/patient-year. Nine-year probability of freedom from mortality (including early mortality) was 85.0% +/- 2.6% overall. There were no cases of structural failure. Thromboembolic events occurred in nine patients, producing a linearized rate of 0.7%/patient-year. Hemorrhage associated with anticoagulant therapy occurred at a rate of 0.8%/patient-year. Therefore, the combined rate of thromboembolic/hemorrhagic events was 1.5%/patient-year. Cumulative overall freedom from thromboembolism and hemorrhage was 91.5% +/- 1.9% at nine years; it was 86.2% +/- 4.3% after mitral and 95.1% +/- 2.0% after aortic valve replacement. Hemolytic anemia was not observed. Endocarditis occurred eight times (0.6%/patient-year), and there were seven cases of perivalvular lead (0.5%/patient-year). At the end of the follow up, 86% of the patients were in NYHA class I. It is concluded that clinical results over a nine-year period are excellent with the Omnicarbon prosthesis.