Recent refinements in pulsed Doppler technology have made possible the noninvasive assessment of hemodynamic function. The application of the Doppler frequency shift principle to study discrete velocity events at a measured distance from the transducer is discussed. The accuracy and limitations of Doppler techniques in determining ascending aortic and peripheral blood flow velocities in infants with various cardiac lesions are examined. Noninvasive assessment of myocardial contractility is also described. Most studies performed to date suggest that pulsed Doppler techniques provide a sensitive approach to the measurement of flow velocity and acceleration in appropriate selected circumstances. However, distinctions between volume flow and flow velocity must be considered in the interpretation of data.