The majority of unresolved problems in the present era of heart surgery are biologic rather than technical. The advances made in total body perfusion, the improvement in the protection of the myocardium in artificially induced cardiac arrest, etc., have made it possible to deal quite successfully with several types of congenital and acquired heart anomalies. The operative results, however, are still discouraging if the procedure is aimed not only at repair of a defect, but at replacement of a malfunction or destroyed vital structure of the heart, as well. A practical application of this problem is the surgical management of valvular incompetence. Valvular insufficiency can be successfully repaired in some instances by valvuloplasty. In most cases, however, the calcific degeneration of the valve tissue makes plastic correction futile. The only effective way to handle such situations seems to be the complete excision and replacement of the valvular apparatus. Different materials