Asplenia and polysplenia are frequently associated with complex cardiac malformations and other visceral abnormalities. These latter may include malrotation of the gut, horizontal liver, interrupted inferior vena cava with azygos continuation, and symmetry of the lungs. The findings on thoracic and abdominal X rays may frequently help one predict the type of splenic abnormality, but this is not invariable. The knowledge of the spleen is helpful in suggesting the most likely cardiac malformations. Forty one patients with proven asplenia or polysplenia coexisting with congenital heart disease were analyzed in detail. In these cases the abdominal or thoracic X rays as well as the angiographic findings were reviewed. The findings were correlated with cardiac catheterizations, surgical operations, and postmortem examinations. Certain characteristics were found to be prevalent in each of these. The presumptive diagnosis from the plain film X rays can be made in classical situations, but it is not as clear cut as one would hope. The fact that this constellation of findings can be seen in cases with a normal spleen is also discussed.