The rapid growth in technology after the demonstration of the clinical utility of M-mode echocardiography has led to instruments providing two-dimensional noninvasive ultrasound examinations of the heart and other organs in real time, with high resolution. These techniques now provide images with a wealth of diagnostic, anatomic, and physiologic information. The clinical application of this technology over the past three or four years in many medical centers represents a most profound change in diagnostic pediatric cardiology, providing noninvasively derived information which can be used to decrease the morbidity and mortality of diagnosis and serial follow-up of children with serious congenital heart disease.