The non-overlapping tilting disc of the Björk-Shiley prosthesis has proved its efficiency in two respects: It provides an optimal orifice to tissue diameter ratio with a favourable rheology both at rest and during exercise even in the smaller valve sizes used for insertion in narrow aortic roots. It accounts for a minimal haemolysis because mechanical crushing of the red cells is minimized by such a non-overlapping closing mechanism. Regurgitation is negligible. The excellent durability of the prosthesis has been clinically testified. Thrombo-embolism has not so far occurred with effective Dicumarol treatment. Aortic valve replacement with the Björk-Shiley tilting disc valve is regarded as an elimination of the volume load of the left ventricle in AI and the pressure load in AS, thereby creating a pre-requisite for a normalization of the pump function of the heart.