Our purpose was to investigate the long term outcome of Hancock bioprostheses at our Hospital. There were 128 bioprostheses, with histopathological study on 17 of them. The 12.8 years follow-up disclosed dysfunction on 48.18% with an annual dysfunction rate of 3.34 +/- 1.3. One half of the patients with prosthetic dysfunction were re-operated. A comparison of our results is made with those of the literature, either with biological or mechanical prostheses.