The 15-year experience (1983-1998) with 1,187 patients who received St. Jude Medical Biocor porcine bioprostheses (a third-generation valve) in the aortic (1,029) or mitral (158) positions was reviewed. Follow up was 99.7% complete. Mean patient age was 69 and 63 years for the aortic and mitral bioprosthesis groups, respectively. Actuarial survival for patients with aortic valve replacement (AVR) was 41% versus 25% for mitral valve replacement (MVR). Freedom from valve-related death was 94% after AVR and 84% after MVR. In total, 51 patients (46 AVR, five MVR) were reoperated on due to structural valve deterioration (SVD) during the 15-year period, with no operative death. Freedom from reoperation due to SVD was 76% for AVR and 92% for MVR; the rate of freedom increased with age in both groups. Actuarial freedom from thromboembolism was 82% and 75%, from anticoagulant-related hemorrhage 85% and 85%, and from prosthetic valve endocarditis 95% and 93% for the AVR and MVR groups, respectively. We conclude that the frequency of valve-related complications is low. The third-generation porcine bioprosthesis appears to be more durable than valves of previous generations.