The performance of three fascia lata valves in aortic position, a Sterling-Edwards, a Ionescu and a valve of our design, was compared in a test chamber with that of a Starr-Edwards valve. Pulsatile pressures and flows of shapes and magnitudes similar to in vivo conditions at the left ventricular and aortic levels were provided by a pulse duplicator system. Mean values ± 1 SD of measurements made on 10 successive strokes of the Starr-Edwards valve were the following: mean total pressure gradient (ΔPv–a): 5.0 ± 0.4 cm H2O, approximated energy loss (E): 269, 530 ± 19,440 erg/stroke, instantaneous energy loss (E): 247,040+10,600 erg/stroke and backward flow (Qbf): 1.3 ± 0.3 ml. The same results for the Sterling-Edwards, the Ionescu and the fascia lata valve of our design, expressed in percent of the Starr-Edwards mean values were respectively for ΔPv–a: 136, 182 and 66%; for 1: 147, 160 and 65%; for E: 208, 215 and 60%; and for Qbf: 131, 308 and 477%. The valve of our design was, therefore, shown to present a significantly smaller loss of energy but a more important