Pheochromocytomas are catecholamine producing tumors of neuroectodermal origin. Diagnosis of pheochromocytoma is significant due to potentially curable hypertension. But they have a significant associated morbidity due to uncontrolled hypertension and mortality since 10% are malignant. From Aug. 1989 to Jul. 1992, 12 patients of our institution had 131I-MIBG scan during work up of suspected primary or recurrent pheochromocytoma. In our studies conclude that 131I-MIBG scan is recommended as the initial localizing study of choice (especially for the detection of extraadrenal disease and postoperative recurrence) as a guide for CT and/or MR and specific functional confirmation of their findings.