Intrapericardial pheochromocytoma. In a 34-year-old man with hypertension and increased urinary catecholamine excretion for 12 years, an m-[131I]iodobenzylguanidine scan and chest computed tomography located an intrapericardial pheochromocytoma in the left atrium. The tumor was excised through a left thoracotomy with cardiopulmonary bypass and circulatory arrest. At 34-month follow-up, blood pressure and urine catecholamine levels were normal. In the 15 cases of intrapericardial pheochromocytoma treated by resection reported in the literature, all 11 survivors were symptom-free except 1 who had residual left atrial tumor and multiple skeletal metastatic lesions. Computed tomography directed by the m-[131I]iodobenzylguanidine scan can be used for detailed location of the tumor. Appropriate surgical approach and use of cardiopulmonary bypass are critical in the resection of these highly vascular tumors. 