Color Doppler echocardiography (CDE) enables visualization of blood flow and of cardiac morphology within color coded two-dimensional images. The diagnostic usefulness of this method in pediatric cardiology has been analyzed based on studies performed in 2414 children. Normal cardiac findings were seen in 769 patients according to the clinical and echocardiographic examinations. Normal diastolic inflow into the ventricles in the apical four-chamber-view is characterized by a similar distribution of the color spectrum across the inflow tracts, blood flowing on the two sides of the heart is completely separated from each other. Normal systolic outflow imaged from parasternal position shows an increase in velocity in the outflow tract passing through the semilunar valves without any change in flow patterns. Heart disease was present in 1645 patients, simple cardiac defects were found in 1473 cases and complex heart disease in 172 cases. Shunt lesions are detectable by the demonstration of blood flow in regions where normally no flow is detectable, flow velocities being pathologically increased in many cases. Diagnostic sensitivity and specificity of CDE as compared to invasive procedures is between 96 and 98%. In left-to-right shunting the shunt flow can be followed into the right-sided cardiovascular regions where its extent is a measure for the size of the shunt as indicated by initial results. In ventricular septal defects, bidirectional shunting is indicative of a rise in pressure in the right ventricle and can be reliably detected with the use of CDE. In valvular stenoses high flow velocities are found in the appropriate time which are associated with turbulence and poststenotic eddies.(ABSTRACT TRUNCATED AT 250 WORDS)