Background and aim of study: The study aim was to review the 15-year results of aortic (AVR) and mitral (MVR) valve replacement with the St. Jude Medical Biocor porcine prosthesis, in order to investigate long-term survival and valve-related complications. Methods: Between January 1983 and January 1998, a total of 1,187 patients underwent either AVR (n = 1,029; mean age 69 years) or MVR (n = 158; mean age 63 years). Follow up (99.7% complete) was monitored in 1998, and all data were analyzed with regard to actuarial valve failure rates. Long-term echocardiographic data were obtained. Results: Cumulative follow up time was 5,049 patient-years (pt-yr) for AVR patients, and 845 pt-yr for MVR patients. Actuarial survival rate at 15 years was 41 +/- 3%, and freedom from valve-related death was 94 +/- 1% for the AVR group; corresponding values for the MVR group were 25 +/- 11% and 84 +/- 6%. The occurrence of structural valve deterioration (SVD) varied with age; older patients were less affected. Freedom from SVD was 76 +/- 7% and 92 +/- 4% for AVR and MVR patients, respectively. Thromboembolism (TE) occurred mainly among the oldest patients, and was most prevalent among those with MVR. Actuarial freedom from TE was 82 +/- 5% after AVR and 75 +/- 7% after MVR. Prosthetic valve endocarditis (PVE) was rare, but caused the only reoperative mortality. Freedom from PVE was 95 +/- 2% after AVR and 93 +/- 3% after MVR. Conclusion: Although the optimal valve substitute remains to be found, this long-term study of a third-generation bioprosthesis showed a low incidence of valve-related complications, especially of valve deterioration. This type of bioprosthesis appears to be more durable than valves of previous generations.