Limited durability is the one of the major disadvantages of bioprostheses, few of which survive beyond 20 years. A 61-year-old male patient was admitted urgently to our institute with acute mitral insufficiency, 24 years after undergoing mitral valve replacement with a 25-mm standard Hancock porcine bioprosthesis for mitral stenosis. Mitral valve reoperation was performed successfully with a mechanical valve. The explanted bioprosthesis showed leaflet perforations and a commissural tear, moderate calcification on the commissures, and pannus overgrowth. The findings in this case suggest that individual patient variables, as well as the design and the construction of the valve, are major determining factors in the rate of valve failure.