The development of pediatric transesophageal ultrasound imaging represents an important advance in the diagnosis and treatment of the child with congenital heart disease. Although primary diagnostic transesophageal studies are seldom indicated in infants and unoperated children, they have an important role in the older child especially where there has been prior cardiac surgery. Diagnostic studies are most appropriate for abnormalities of venous return, the atria, atrioventricular valves, and the left ventricular outflow tract. Two other important areas in which transesophageal imaging is playing an increasing role in the treatment of the pediatric patient is in monitoring interventional catheterization and in the intraoperative and immediate postoperative monitoring of surgical repair.