Six cases of Ebstein's malformation are reported. The notable clinical features seen in four patients were gross enlargement of the
heart, venous congestion and marked hepatosplenomegaly. There was complete heart block in one patient and auricular fibrillation in the remaining three. The unusual pathologic features in the four cases that came to necropsy were the large pericardial effusions associated with the cardiomegaly, the absence of an atrial septal defect or patent foramen ovale, the gross enlargement of liver with cirrhotic changes and the large spleen. Histologic examination of heart muscle revealed certain unusual features which are described.