Although several excellent roentgenologie and clinical papers have dealt with Ebstein's anomaly of the tricuspid valve (1–6), little attention has been given to the angiocardiographic appearance of the infundibulum or outflow tract of the right ventricle. In several cases of Ebstein's anomaly of the tricuspid valve recently studied, an unusual phenomenon in respect to the expansile nature of the right ventricular infundibulum was observed. So unique was this angiocardiographic finding that additional cases were reviewed to determine whether or not it was specific for Ebstein's anomaly of the tricuspid valve. The purpose of this paper is to describe the angiocardiographic findings relating directly to the right ventricular infundibulum in 12 cases of Ebstein's anomaly studied over the past three years. The source material for this paper is from The St. Louis Children's Hospital, and each case was studied in the Mallinckrodt Institute of Radiology, both institutions being within The Washington University School of Medicine. Material Selective right ventriculograms were reviewed in 12 cases of Ebstein's anomaly. Four of the 12 cases were proved by necropsy, and the remaining 8 were documented on the basis of angiocardiographic and hemodynamic data considered diagnostic for this condition. The youngest patient was four months old, the oldest fifteen years; 8 were males, 4 females. Results Selective right ventriculography demonstrated an anomalous, thickened inferiorly displaced tricuspid valve with varying degrees of tricuspid valve insufficiency. In addition, the“contractile synchrony” of the atrialized portion of the right ventricle was observed in each case (2, 3). Angiocardiographic details for Ebstein's anomaly, in this paper, will be confined to the right ventricular (RV) infundibulum. Signs regarding the tricuspid valve will be dealt with in the legends. In 10 of the 12 cases studied, the RV infundibulum exhibited an extreme degree of volume variation. The period of peak dilatation occurred during ventricular diastole, and maximum contraction during end-systole (Figs. 1–5). At peak diastole, the superior aspect of the infundibulum rose above the superior aspect of the pulmonary trunk (Figs. 1–3). The latter phenomenon became manifest in the frontal view as a ball-like density within another round density (an angiocardiographic finding which led us to coin the term of“double-ball sign” of Ebstein's anomaly; Figs. 1–3). In one case (Fig. 4), the RV infundibulum exhibited considerable volume variation, but the superior aspect of the infundibulum did not rise above the pulmonary trunk.