This study aimed to demonstrate the morphologic findings in a series of explanted Hancock II porcine bioprostheses, among the first clinically used prostheses to have been treated with an antimineralization agent. The prostheses were analyzed by gross and dissection microscope examination, radiography and light microscopy. The bioprostheses showed a combination of structural degeneration, with cusp tears and calcification, pannus and infective endocarditis. The incidence of calcification appears to be lower than in previous (Hancock standard) series, and lower at the mitral site. Significant pannus was seen at both sites. Mitral-site outflow surface pannus may be related to the mitral valve (native) conserving procedure. While the morphologic findings are similar to those in other series of porcine bioprostheses, the incidence of significant calcification (especially at the mitral site) is lower, at up to 11 years post implantation. The incidence of significant pannus is high, but this is obviously a non-valve-related complication.