In this review I concentrate on issues related to prosthetic valves themselves: their development, performance, and durability. For example, mechanical failure or tissue deterioration appear to be intrinsic properties of the valve and are therefore central to my topic, whereas the development, diagnosis, and management of endocarditis are largely independent of the type of prosthesis and are thus not dealt with here. Other outcomes such as stroke are also determined by factors other than the choice of valve, as was cogently argued in papers published during the past year. The papers on tissue valves have a common theme: they document the inevitability of tissue failure, too early for acceptable use other than in old age. The mechanical valves that have stood the test of time have done so because they do not fail.