Of 699 patients with 900 bioprostheses, who lived longer than six months, three cases of early perforation of bioprosthetic leaflets are reported. In two cases the cut ends of the suture used for valve insertion had perforated the bioprosthetic cusps from repeated trauma. Insertion of the sutures in the periphery of the sewing ring and cutting the sutures flush with the knots should avoid this complication. The third case showed massive collagen breakdown with destruction of most of the cusp tissue. A possible explanation for such a massive early tissue breakdown could be an inadequate collagen fixation by glutaraldehyde.