Using real-time, three-dimensional (3D) color Doppler, experimental studies were performed to quantify velocity in the out flow tract from cross-sectional, short mis images. In vitro experiments showed an excellent linear correlation between the reference pulsed wave (PW) Doppler and 3D color estimates of the peak velocities (r = 0.98). In an animal experiment, 3D peak flow velocities showed a reasonably good agreement with reference peak velocities by PW Doppler (r = 0.76, delta = +11.6 %). The spatial mean velocity by 3D showed a good linear relationship with PW peak velocity, but with an anticipated underestimation (r = 0.81, delta = -43 %) due to the non-uniform velocity profile. Real-time, color 3D echocardiography was capable of quantifying velocities accurately, permitting the calculation of flow volume without any geometrical assumptions about flow distribution.