Nine patients with Ebstein's anomaly of the tricuspid valve were studied by two-dimensional echocardiography, using the standard long and short axis views as well as the apex four chamber view. With this latter view, the displacement of the tricuspid valve into the right ventricle was clearly seen in all nine cases of Ebstein's anomaly and was not noted in a control population. The severity of the tricuspid displacement was assessed by comparing the position of the mitral and tricuspid valves relative to the cardiac apex. The apex four chamber view allowed visualization of the atrioventricular (AV) ring simultaneously with the displaced tricuspid valve, and therefore the size of the "atrialized" right ventricle, true right ventricle and right atrium could be determined. These dimensions compared favorably with angiography.