The typical textbook description of Ebstein's anomaly of the heart usually singles out and emphasizes the downward displacement of septal and posterior leaflets of the tricuspid valve. An anatomic reappraisal of this uncommon anomaly suggests that other structural abnormalities of import should be equally stressed. Among the 15 well preserved autopsy specimens in this series, enlargement of the right atrioventricular (A-V) junction and malalignment of the giant and sometimes muscularized anterior leaflet of the tricuspid valve were consistently found. In addition, massive aneurysmal dilation of the right ventricle was present in almost two thirds (9 of 15) of the hearts. Our observations raise the possibility that abnormal embryonic development of the right A-V junction may be the primary event that leads to malformation of the tricuspid valve apparatus.