Pheochromocytomas are rare tumors that originate in chromaffin tissue and produce their distant variant effects by secretion of catecholamines, tending to mislead the emergency physicians to a wrong diagnosis. Therefore, we analyze the clinical cardiovascular manifestations in patients with pheochromocytoma to improve the diagnostic ability of the emergency physicians. All patients presenting to the Chang Gung Memorial Hospital between January 1993 and December 1997 with a final diagnosis of pheochromocytoma had their charts reviewed. The data of 25 patients including age, sex, adrenergic stimulation presentations, electrocardiographic changes, location of the tumor, and complications were analyzed. Hypertension was the most important major manifestation and fluctuation of blood pressure drew our attention to the possibility of pheochromocytoma. Six patients had abnormal electrocardiographic ST-T segment changes. Five of them had chest pain which prompted them to undergo coronary angiography before surgery, because acute coronary syndrome (unstable angina and acute myocardial infarction) was suspected initially. However, all of them turned out to have normal coronary arteries. Right-sided pheochromocytoma was found in three of these five patients. We should maintain high index of suspicion for pheochromocytoma in patients presenting with chest pain, fluctuating blood pressure, and ischemic electrocardiogram (ECG) changes despite any typical isoenzyme changes. Pheochromocytoma should also be included in the differential diagnosis of acute coronary syndrome because acute catecholamine secretion may induce chest pain and abnormal ECG changes mimicking an ischemic episode. The right-sided pheochromocytoma may present more striking electrocardiographic abnormalities and clinical manifestations.