To improve biocompatibility and durability of valve prostheses, "tissue engineering" is being investigated to develop an ideal replacement heart valve. Our approach is to extract all cells from porcine heart valves leaving behind only a collagenous matrix. The remaining collagen framework is reinforced using slowly resorbable, biodegradable polymers poly(4-hydroxybutyrate) and poly(3/4-hydroxybutyrate). To determine if the bioresorbable polymer/collagen composite possesses the mechanical properties necessary for a replacement heart valve, pulsatile flow studies were carried out in a pulse-duplicator. Instrumentation allows simultaneously measurement of flow rate and pressure drop across the valve, while leaflet motion is assessed by high-resolution video morphometry (500 frames/sec). Matrices at various stages in the tissue engineering process were tested. Strictly decellularized valves performed like normal valves with minimal leakage. The mechanical properties of the polymer/collagen composite valves varied markedly, depending on the type of polymer as well as the polymer concentration in the coating suspension. Further development is necessary to achieve an effective polymer/collagen coupling for dynamic usage.