Total anomalous pulmonary venous connection can be diagnosed by cross sectional echocardiography. Information is, however, lacking concerning the diagnostic accuracy of this imaging method and any factors which may influence it. To predict the pulmonary venous connection 463 patients with congenital heart disease who had angiographic confirmation were prospectively examined. Total anomalous pulmonary venous connection was present in 34 (7%) patients and correctly detected in 33 (97% sensitivity). There were two false positive results (99% specificity). All 23 patients with atrial situs solitus with or without associated congenital heart defects were correctly detected. One false negative result occurred in a patient with right atrial isomerism and complex congenital heart disease with decreased pulmonary blood flow. Diagnosis of the type of total anomalous pulmonary venous connection, including the site and other anatomical details, was analysed and was correct in 24 of 34 (71%) patients. Errors included incorrect prediction of the site of total anomalous pulmonary venous connection in five patients with right atrial isomerism, atrioventricular canal defect, and pulmonary atresia, details of confluence interconnection in three of four patients with the mixed type of connection, undiagnosed pulmonary venous obstruction in three of the patients with right atrial isomerism, and failure to predict common pulmonary vein atresia in one patient. Factors which were related to incorrect echocardiographic diagnosis were abnormal atrial situs, mixed total anomalous pulmonary venous connection, and associated congenital cardiac defects, whereas age, weight, sex, clinical condition, and time during the study were not related. It is concluded that cross sectional echocardiography can be used to diagnose accurately total anomalous pulmonary venous connection. This method can be the definitive imaging and diagnostic method in symptomatic infants with total anomalous pulmonary venous connection who have atrial situs solitus, unifocal pulmonary venous connection, and no evidence of other major congenital cardiac defect.