Twenty-six patients with Ebstein's anomaly were classified into three types according to their clinical features, heart catheterization data, angiocardiographic and anatomical findings which were obtained on surgery or autopsy. The hemodynamics in each type were discussed. 1. Tricuspid Stenosis Dominant Type. Eight patients, who were cyanotic and had severe symptoms, mild to moderate cardiomegaly, and the "double-ball sign" on angiocardiography were classified into this type. A pressure gradient across the tricuspid valve was demonstrated in 5 patients. 2. Tricuspid Insufficiency Dominant Type. Four cyanotic patients, who had mild symptoms despite the severe cardiomegaly were grouped into this type. The "double-ball sign" was found in all. In three patients, incompetent tricuspid valve was observed. Tricuspid insufficiency necessitates the volume overwork of the right atrium and the functioning right ventricle, resulting in severe dilatation. 3. Mild Type. Fourteen patients who showed no or mild cyanosis, no or mild symptoms, and mild to moderate cardiomegaly, were classified into this type. It is considered that the adequate cardiac output in these patients is attributable to the good function of the tricuspid valve.