Between November 1977 and October 1980, 54 patients underwent valve replacements with porcine bioprostheses at Hyogo Kenritsu Amagasaki Hospital. The late complications and the long term durability of 53 porcine bioprostheses were documented in 48 patients after discharge (34 mitral, 7 aortic, 2 tricuspid, and 5 multiple, consisting of 38 Hancock, 15 Carpentier-Edwards prostheses). Cumulative duration of follow-up is 420 patient-years. The valve related late mortality was 0.52%/patient-years. There were 6 thromboembolic events (1.6% patient-years), only 1 episode of endocarditis (0.26%/patient-years). Valve dysfunction is defined as stenosis or regurgitation by echocardiogram or cardiac catheterization. There were 21 instances of porcine bioprosthetic dysfunction (6.6% patient-years). Freedom from valve dysfunction at 12 years was 24.4%. There were 17 valves of mitral bioprosthetic dysfunction (6.4% patient-years). The incidences of mitral stenosis (MS), mitral regurgitation (MR), and paravalvular leakage were 4.5, 3.6, and 0.7%/patient-years respectively. Freedom from MR was higher than MS at 8 years. The 14 patients were needed reoperation due to valve dysfunction (3.6%/patient-years). We concluded that the porcine bioprostheses showed a high incidence of valve dysfunction at 7 to 8 years after operation, we presently choose mechanical valve in most cases.