The reliability was evaluated of two dimensional echocardiography in distinguishing double outlet right ventricle from other anomalies of the great arteries. Accordingly, a combined retrospective and prospective study was conducted in 13 children with double outlet right ventricle, 12 with tetralogy of Fallot, 13 with complete d-transposition of the great arteries, 5 with congenitally corrected I-transposition and 2 with truncus arteriosus. Echographic findings using a standard long axis view in all subjects with double outlet right ventricle included (1) inability to identify a great artery arising from the left ventricle, and (2) lack of continuity between the anterior mitral leaflet and any semilunar valve. In the short axis view constant findings were (1) simultaneous imaging of both great arteries in an anterior location with the ventricular septum identified posteriorly on sweeping into the left ventricle, and (2) lack of a clockwise wraparound of the aorta by the right ventricular outflow tract. Imaging revealed that the great arteries were side by side in seven patients d-malposed in three and l-malposed in two. A modified left precordial tomographic view demonstrated both great arteries arising from the right ventricle in four of nine patients not treated surgically. In four patients with surgically repaired double outlet right ventricle, the left ventricular outflow tract had a tunnel-like configuration in the long axis view. These findings were diagnostic of double outlet right ventricle in all patients and accurately differentiated the malformation from other anomalies of the great arteries.