Ebstein's malformation is a congenital anomaly of the tricuspid valve and right ventricle that is characterized by several features, each of which can exhibit a spectrum of malformation. The first is adherence of the leaflets of the tricuspid valve to the underlying myocardium, this representing failure of delamination during development. This feature involves the septal and inferior leaflets, but rarely the anterior leaflet (Fig. 1). The second feature is anterior and apical rotational displacement of the functional annulus (Fig. 2). The third abnormality is dilation of the “atrialized” portion of the right ventricle, with variable degrees of hypertrophy and thinning of the wall. The fourth finding is redundancy, fenestrations, and tethering of the anterior leaflet. A fifth abnormality is dilation of the right atrioventricular junction, this being the true tricuspid valvar annulus. The final feature is variable ventricular myocardial dysfunction. Each heart with Ebstein's malformation is different, and there is an infinite variability that can occur with the above mentioned characteristics. These anatomical and functional abnormalities cause important tricuspid regurgitation, which results in right atrial and right ventricular dilation, and atrial and ventricular arrhythmias.