Early scintigraphy, that obtained 6 hours after intravenous administration of a low dose of 123I-metaiodobenzylguanidine (111 MBq) was evaluated for diagnostic efficacy. The accumulation of 123I-MIBG in the tumor masses of nine patients with pheochromocytoma and one patient with cortical adenoma were noted. The smallest pheochromocytoma visualized was 3 cm in diameter. The hepatic uptake of this radiolabeled compound was helpful to understand the anatomical position of the abnormal uptake. Three of five postoperative cases of pheochromocytoma showed uptake in the metastasis in the skeleton or recurrences in the neck or contralateral adrenal gland. No ectopic pheochromocytoma was found in the pelvic cavity. Faint accumulation in the normal medulla was noted in 45% of the cases. The present results demonstrate that superior images can be obtained in scintigrams takes 6 hours after administration of a lower dose of 123I-MIBG.