Comparative long-term performance characteristics of St. Jude Medical (SJM) and bioprosthetic valves were conducted retrospectively for patients who under-went prosthetic valve replacement in the right side of the heart from 1975 to 1988. Fifty-four patients received either SJM (n=18) or bioprosthetic (n=37) valves. The cumulative follow-up for SJM valves was 91 valves-years (range 3.9 to 7.2 years) and that for bioprostheses was 282 valve-years (range 1.3 to 14.8 years). Follow-up rate was 100%. The actuarial survival rate excluding hospital deaths at 5 years was 81±10% for SJM and 97±3% for bioprosthetic valve recipients (p=ns). The rates of freedom from thrombosis or anticoagulant-related hemorrhage, structural valve failure, prosthetic valve endocarditis, reoperation, and overall valve-related complications at 5 years were 72±11%, 100%, 100%, 83±9%, and 72±11% for SJM valve recipients, and 100%, 97±3%. 97±3%, 94±4%, and 94±4% for bioprosthetic valve recipients, respectively. Structural valve failure, prosthetic valve endocarditis and reoperation occurred at a similar incidence in each of the two types of prostheses. Thrombosis and overall valve-related events occurred more frequently in SJM valve recipients (5.5±2.5 vs 0%/valve-year; p<0.02, 6.6±2.7 vs 1.1±0.6%/valve-year; p<0.03, respectively). The bioprosthetic valve which did not need warfarin anticoagulation therapy had low incidence of valve-related complications and showed good long-term durability even in the younger age group. The bioprosthetic valve was superior to the SJM valve in the right side of the heart.