Neuroblastoma is a lethal and not uncommon tumor in childhood. Early detection and display of the spread of the tumor is highly desirable for proper treatment. Nine children suspected of having neuroblastoma were examined by 131I-meta-iodobenzylguanidine (131I-MIBG) scintigraphy. In two recent studies 123I-meta-iodobenzylguanidine (123I-MIBG) was used. A primary adrenal neuroblastoma was correctly identified in 3 cases. In 2 patients additional tumor sites were found. In one patient, who was in complete remission, no pathological accumulation of 131I-MIBG was found. 131I-MIBG scintigraphies were also normal in 4 patients with other types of tumor. In one girl with a large adrenal neuroblastoma high uptake of 131I-MIBG was observed. She received two therapy doses of 131I-MIBG (1300-2800 MBq) with curative intention giving a total absorbed dose in the tumor of approximately 90 Gy. In spite of high retention of radioactivity in the tumor, regression did not appear, but her general condition was improved. In the present study images of superior quality were obtained by 123I-MIBG scintigraphy. It is concluded that scintigraphy with 131I- or 123I-MIBG should be used for primary visualization and control of neuroblastomas.