Angiography of the superior systemic veins was performed on 510 patients with congenital heart disease. An analysis of these angiograms was carried out and a simple angiographic classification of superior vena caval anomalies is presented. Eleven per cent of cases had complete bilateral superior vena cavae, a frequency of occurrence higher than that previously reported. An analysis of associated congenital heart lesions revealed a higher than average association of bilateral superior vena cavae with atrioventricular septal defects and double-outlet right ventricle, but this was seen rarely in cases of transposition of the great arteries. Bilateral superior vena cavae also occurred very frequently (72%) in patients with situs abnormalities. Femoral vein catheterisation is likely to facilitate diagnosis and appropriate radiological signs are discussed.