From 1983 to 1992, 366 patients received 407 Mitroflow pericardial bioprostheses at our institution. Mean age was 62 +/- 14 years (range: 15-86 years). There were 229 isolated aortic valve replacements (AVR), 96 isolated mitral valve replacements (MVR), 39 double mitral and aortic valve replacements (DVR) and four tricuspid replacements. Mean follow up was 6 +/- 2.33 years ranging from 1.67 to 10.9 years. Total follow up was 1791 patient-years. Overall survival was 77.2 +/- 2.2% at five and 56.2 +/- 6.4% at 10 years. It was 74 +/- 3% and 56.2 +/- 5.3% after AVR, 78.3 +/- 4.4% and 55.7 +/- 8.8% after MVR, 81 +/- 6.4% and 36.6 +/- 16.5% after DVR at five and 10 years, respectively. Freedom from structural valve deterioration (SVD) was 95 +/- 1.2% and 36.7 +/- 8.1% at five and 10 years for all valves, 96.9 +/- 1.3% and 39.2 +/- 9.8% for AVR, 91.7 +/- 3.2% and 36.4 +/- 10% for MVR. There was no difference in freedom from SVD between AVR and MVR. The freedom from SVD in patients older than 70 years of age was 100% and 93.9 +/- 5.8% at five and 10 years, respectively. Freedom from reoperation was 94.7 +/- 1.37% and 28.36 +/- 7.5% at five and 10 years for all valves, 96.2 +/- 1.5% and 38.6 +/- 9.7% for AVR, 91.7 +/- 3.2% and 36.4 +/- 10% for MVR. The denaturation process did not lead to acute hemodynamic deterioration. Pathologic findings were cuspal tears (one or more) associated with structural tissue changes.(ABSTRACT TRUNCATED AT 250 WORDS)