Eight heart specimens were examined that had concordant connections of the cardiac segments and exhibited Ebstein's malformation. The displacement of the leaflets of the tricuspid valve from the atrioventricular junction varied from minimal and isolated involvement of the septal leaflet to involvement of the mural and anterosuperior leaflets as well. This resulted in a wide range of physiologic "atrialization" of the right ventricle. The distal insertion of the valve leaflets also exhibited a spectrum of malformation. At one end the insertion was the normal focal variety, allowing free communication between the atrialized and functional parts of the right ventricle. At the other end there was abnormal linear attachment of the anterosuperior and mural leaflets to an anomalous muscular shelf at the junction between the inlet and apical trabecular portions of the right ventricle. The anteromedial commissure between the anterosuperior and the displaced septal leaflets provided a "keyhole" communication between the two ventricular compartments. Between these extremes were cases in which hyphenations along a locus of linear attachment allowed additional communications between the ventricular compartments. In light of these anatomic observations, cineangiograms of 26 patients with Ebstein's malformation were reviewed retrospectively. It was possible to classify the patients into three groups with focal, hyphenated and linear attachment, respectively. Size, ejection and displacement indexes of the functional right ventricle measured from the angiograms suggested that the severity of the malformation increased from focal attachment through hyphenated to linear attachment. Clinical observations relative to symptoms (cyanosis at rest, reduced exercise tolerance) and outcome supported this morphologic-angiographic grading.