Materials and methods: Between 1984 to 1994, 136 patients underwent primary and isolated aortic valve replacement with 79 Carbomedics and 57 St. Jude prostheses. Results: Age ranged from 16 to 67 year(mean : 44.5${pm}$12.7 years). Statistically significant differences in preoperative clinical characteristics between two groups were not found. There was one early death in the St. Jude group and none in the Carbomedics group. Early prosthetic valve-related complications including death were not significantly different between the two groups(p value= 0.572). One hundred thirty five early survivors were followed for a total of 354.2 patient-years(mean=31.5${pm}$16 months). In the CarboMedics group, actuarial survial rate at 5 years was 97.1${pm}$1.9%, and in the St. Jude group, it was 95.9${pm}$2.8%. In the CarboMedics group, actuarial free rate from all valve-related events at 5 years was 92.1${pm}$3.1%, and in St. Jude group, it was 89.8${pm}$5.0%. Conclusion: We conclude that early and late results after performing isolated aortic valve replacement with CarboMedics and St. Jude valve are not significantlly different.