We present a case of Ebstein's anomaly revealed by symptoms occurring at high altitude. A 63 year old male with no previous symptoms of cardiovascular disease developed acute severe shortness of breath when walking up a flight of stairs at an altitude of 2500 m. Echocardiography showed apical displacement of the tricuspid valve. Exercise capacity at sea level was normal, as were oxygen saturation at rest and maximal exercise. We think that the patient's symptoms can be explained by increased afterload on the right ventricle during exercise at high altitude. The functional capacity of the small right ventricle may then be exceeded and symptoms manifest.