This case report describes the peri-operative management of a 65-year-old man with an unsuspected pheochromocytoma. He underwent emergent surgery for a rupturing abdominal aortic aneurysm. During surgery his blood pressure changed dramatically and was resistant to drug treatment. A pheochromocytoma was suspected, but the emergency precluded immediate investigation. A second hypertension episode occurred in the intensive care unit, and CT revealed an abnormal adrenal mass. Surgery for the pheochromocytoma was carried out successfully later, with the hypertension being managed very carefully. We considered that exposure to extraordinary catecholamine levels from the pheochromocytoma might have contributed to the development of the abdominal aortic aneurysm.