The increasing popularity of Doppler echocardiography in recent years has stemmed from the combination of Doppler with two-dimensional echocardiography, and from the Doppler capability for flow velocity measurement. In the past decade, Doppler instrumentation has evolved from single probe A- and M-mode systems with non-quantitative Doppler output, into multi-faceted instruments combining two-dimensional echo, M-mode echo, with both pulsed and continuous wave Doppler. In the field of pediatric cardiology, quantitative Doppler applications have proven most useful in noninvasive measurement of the severity of obstruction at aortic and pulmonic valves, and across pulmonary artery bands. High accuracy is enjoyed using either continuous wave, or high pulse repetition pulsed wave, Doppler. Additional quantitative applications include estimation of volume aortic flow (cardiac output), and comparison with volume pulmonic flow (pulmonary to systemic flow ratio). Through evaluation of specific disturbances of blood flow (timing, location, direction, duration), qualitative aspects of Doppler continue to provide sensitive and specific diagnosis of valvular disease, as well as shunt lesions such as atrial and ventricular septal defect, and patent ductus arteriosus. Qualitative Doppler offers 'semi-quantitation' of the severity of lesions based on demonstration of breadth and extent of the individual flow disturbances. The addition of Doppler flow information to the information available from conventional M-mode and two-dimensional echo has led to a comprehensive cardiac ultrasound capability. Information previously available only from invasive study (severity of gradient, shunt, regurgitation) is now available noninvasively; the impact upon current and long-term aspects of patient care should prove considerable.