The development of a system that images intracardiac anatomy cross-sectionally while simultaneously displaying intracardiac blood flow in realtime has the potential of increasing diagnostic capabilities in the evaluation of congenital heart lesions. This would translate into the ability to visualize intracardiac lesions not identified by standard M-mode, two dimensional (2-D), pulsed, and continuous wave Doppler modalities. A review of 1000 consecutive studies in our laboratory was performed. Doppler color flow mapping was performed in each case after complete segmental analysis by 2-D and Doppler echo. Identification of intracardiac lesions or abnormalities of blood flow by Doppler color flow mapping, not appreciated on routine 2-D/Doppler studies included ventricular septal defect (VSD) (n = 24), atrial septal defect (n = 4), mitral regurgitation (n = 13), tricuspid regurgitation after VSD closure (n = 5), tricuspid regurgitation in association with atrial septal defect (ASD) (n = 7), residual ventricular septal defect after surgery (n = 10), pulmonary insufficiency (n = 4), aortic insufficiency (n = 4), and patent Blalock-Taussig shunt (n = 2). Identification of multiple ventricular septal defects in two patients and the presence of a large left-to-right shunt across an atrial septal defect in the presence of septal aneurysm formation was also aided by Doppler color flow. Use of color flow to identify areas of maximal velocity and turbulence greatly enhanced continuous wave Doppler measurements by directing placement of the Doppler beam within the flow areas.