Although rare, pheochromocytomas are potentially lethal tumors. Thus, it is important that physicians be able to diagnose these tumors. The definitive diagnosis of a pheochromocytoma rests on demonstrating catecholamine overproduction. Once the diagnosis is established, computed tomography scan, magnetic resonance imaging, and metaiodobenzylguanidine studies are utilized for localizing the tumor. This paper reviews the biochemical and radiologic studies useful for evaluating a patient for the possibility of a pheochromocytoma.