The anesthetic management of patient with pheochromocytoma is often difficult even when a clear-cut preoperative diagnosis has been made. We experienced a patient with a gastric polyp and an unsuspected pheochromocytoma which presented with transient hypertension during general anesthesia for an elective subtotal gastrectomy. The patient developed severe hypertension and arrhythmia leading to cardiac arrest just after the skin incision. This case illustrate the value of preoperative evaluation in a patient with transient hypertension.