Ebstein's anomaly (EA) is a rare congenital heart disease of the tricuspid valve, and less than 5% of patients with EA survive beyond the age of 50. We report two unoperated cases of EA in adult patients aged over 50 years. Two patients, a 70-year-old Japanese woman and a 59-year-old Chinese woman, were referred to us for tachyarrhythmias. Transthoracic echocardiography demonstrated apical displacement (>8 mm/m(2) body surface area) of the septal leaflet of the tricuspid valve from the atrioventricular ring with tricuspid regurgitation in both patients. The former suddenly expired 20 months later after suffering from repetitive supraventricular tachyarrhythmias and/or heart failure, and the latter is alive with minimal signs of heart failure 12 months after the diagnosis of EA. Although the natural history of EA is extremely variable, these two patients are exceptional in that they tolerated EA well for over 50 years without any surgical intervention.