The Carbomedics valve prosthesis is a second generation mechanical prosthesis with a double hemi-disc. This study analysed long-term morbidity and mortality associated with this prosthesis. Between 1987 and 1996, 397 prostheses were implanted, 306 aortic, 42 mitral and 26 double replacements (3 combining a Carbomedics aortic prothesis with a mitral valve from another type) in 370 patients with a mean age of 62 (range 4 to 88 years). The global operative mortality was 7.4%. A questionnaire sent to treating cardiologists, general practitioners and patients updated the prospective data base of the cardiac surgical department. The follow-up was 99%, representing a total of 1244 patient-years with an average of 41 months (range 1.1 month to 9.9 years). The 1, 3, 5 and 7 year survival (operative mortality included) was 88%, 80%, 76% and 69.6% respectively. Haemorrhagic complications were the most common (17 cases, 1.36% per patient-year) and 11 thromboembolic episodes were observed (0.88% per patient-year) with a higher incidence (p < 10-4) in mitral valve replacement (3.8% in patient-year). The other complications observed were: 5 aseptic paravalvular leaks (0.4% per patient-year) and 5 prosthetic valve infections; no structural alterations were observed. In all, ten reoperations (0.8% per patient-year) were required for prosthetic valve complications. This study shows the reliability of Carbomedics valve prostheses with a low complication rate comparable to that of other modern mechanical valve prostheses.