Autopsy and antemortem two-dimensional echocardiographic findings were compared in 30 cases to assess the predictive accuracy of two-dimensional echocardiography in complete transposition of the great arteries, and thus its potential for replacing or altering an invasive examination. These cases represent consecutive autopsy cases of transposition between January 1978 and December 1982. Ages at echocardiographic study ranged from 1 day to 15.5 years (median 8.5 months). Transposition of the great arteries had been diagnosed correctly in every case, and all associated anomalies identified by two-dimensional echocardiography were confirmed at autopsy. Several additional anomalies not found by two-dimensional echocardiography were apparent at autopsy; however, most were minor and insignificant. The only potentially significant false negative findings were one ventricular septal defect, two small atrial septal defects, one mitral valve anomaly, one tricuspid valve anomaly, three instances of patent ductus arteriosus and four instances of persistent left superior vena cava. Although significant pulmonary stenosis was predicted correctly, the site of stenosis was not accurately defined in four cases. Two-dimensional echocardiography is a reliable means of diagnosing transposition of the great arteries. It can limit the need for angiocardiography in the neonate; and in older infants and children, it should be used to complement cardiac catheterization and angiocardiography. The latter may be indicated, especially before surgical repair, to better define small ventricular septal defects, site of pulmonary stenosis, atrioventricular valve insufficiency and patent ductus arteriosus.