A new flow model with left ventricular and aortic chambers composed of an agar gel which mimics the ultrasound characteristics of biological tissues was developed for comparative in vitro hydrodynamic and Doppler ultrasonic evaluation of aortic prosthetic heart valves. An electromagnetic flowmeter and a physiological monitoring system provide the flow and pressure signal measurements. The Doppler ultrasonic evaluation is performed with an Ultramark 9 HDI ultrasound system and a 3D ultrasound imaging system. The model was designed to allow assessment of prosthetic valve performance by conventional and 3D color Doppler velocity measurements using computer-controlled scanning of the aortic chamber with an ultrasound probe. The experimental results demonstrate that this new flow model can provide accurate comparisons of hydrodynamic parameters of prosthetic heart valves derived from Doppler and catheter measurements, both under steady and pulsatile flows.