Pheochromocytoma is a surgically curable, functioning chromaffin cell tumor, causing hypertension and metabolic derangements. A 36 year old female was admitted presenting striking electrocardiographic changes mimicking ischemic heart disease and wide fluctuations of blood pressure. Coro- nary angiographic findings were normal. Urinary excretion of catecholamine and its metabolites were elevated, and pheochromocytoma was strongly suspected. Abdominal CT scan revealed a huge, round mass in the left upper abdomen. After surgical removal of the mass, the patient has become totally asymptomatic with complete disappearance of the electrocardiographic abnormalities and the fluctuations of blood pressure, and urinary excretion of catecholamines have been normalized.