“…As an alternative to prosthetic valves with their thromboembolic problems, aortic allograft valves have been used with success in large numbers in the aortic region (McDonald et al, 1968;Barratt-Boyes, 1971;Yacoub, Knight, Towers, and Somerville 1973;Layton et al, 1973) and to a lesser extent in the mitral region (Graham, Schroeder, Daily, and Harrison, 1971;Lennox et al, 1971; Barratt-Boyes et al, 1972;Angell, Wuerflein, Chun, and Shumway, 1973). The behaviour of the aortic valve when used as a mitral valve replacement has also been fairly extensively investigated in animals (Howard, Willman, and Hanlon, 1960;Heimbecker et al, 1962;McKenzie et al, 1966;Suzuki and Kay, 1966;Angell, Wuerflein, and Shumway, 1967;Hubka, Siska, and Holec, 1967;Weldon, Ameli, and Morovati, 1967;Braunwald, Fuchs, and Bonchek, 1968;Sugie et al, 1969).…”