Twenty surgical and two autopsy cases of pheochromocytoma are reviewed. Preoperative diagnoses were reliably determined by urinary catecholamine excretion studies in most cases. Arteriography and computed axial tomography were the most consistently useful studies in localization of tumor. Preoperative alpha blockagde with phenoxybenzamine, although incomplete in most cases as judged by intraoperative hypertension or postexcision hypotension, appear to have been beneficial as there was not operative mortality. Continued hypertension after tumor removal can be expected in 25 percent of patients despite normalization of catecholamine excretion studies. The cause of this is unknown, but vigilance for recurrent tumor should be maintained.