Until March 1991, 435 St. Jude Medical valves and 330 CarboMedics valves were implanted in 358 and 251 patients, respectively. 300 patients were male and 309 were female with the mean age of 35.6 years[from 2 month to 68 years]. 458 valves were implanted in the mitral, 272 in the aortic, 25 in the tricuspid, and 10 in the pulmonic position. Postoperatively, all patients except for very young patients were given coumadin with or without dipyridamole for anticogulation Operative mortality was 7.3%[45 deaths per 618 operations]. A total follow-up of 1244.8 patient-years was achieved for the operative survivors with a follow-up rate of 96.8%, [mean follow-up period=26.3 months /patient, ranging from 1 to 80 months]. Functional improvement was evident; 66.7% of these patients were in NYHA functional class III or IV preopratively, whereas 98.4% are in class I or II pos-toperatively. There occurred 13 late deaths[7 valve-related] and 55 valve-related complications. Linearized rates of late death and valve-related complications were 1.0%/ patient-year, 4.42%/patient-year, respectively. Rates of thromboembolism, anticoagluation-related hemorrhage were 1.12%/patient-year, 1.69% /patient-year, respectively. Actuarial survival at 5 years is 96.0% and complication-free survival at 5 years is 83.9%. No difference in survival and incidence of complications was found between the St. Jude and CarboMedics valves. On the basis of this experience, we believe that the pyrolytic carbon bileaflet mechanical valves are safe and preferable choice among current valve prostheses.