Thirty-one children with stage III and IV neuroblastoma were studied with iodine-131 metaiodobenzyl-guanidine (MIBG) scintigraphy, technetium-99m medronate scintigraphy, skeletal plain radiography, and computed tomography (CT) before and after bone marrow transplantation (BMT). Twenty-six pre-BMT and 90 post-BMT studies were reviewed. Fourteen patients were alive without tumor, and one patient died at 4 months while free of tumor. I-131 MIBG scans obtained before and after BMT were negative in eight of the 15 patients. Seven had positive I-131 MIBG scans obtained before BMT that became negative after BMT. Six of 15 patients had small, questionable lesions on CT scans of the chest or abdomen that never increased in size, and the I-131 MIBG scans remained negative. Sixteen children had progressive disease or relapse, including four in whom I-131 MIBG scans showed new abnormalities, four with persistently positive I-131 MIBG scans, and three who had negative I-131 MIBG scans at relapse. Two of the 16 patients initially had small lesions seen on abdominal CT scans that were not seen on I-131 MIBG scans; mass lesions were later seen at CT in these locations. Detectable I-131 MIBG uptake in abdominal and thoracic lesions was related to the diameter of the lesion. Both I-131 MIBG scintigraphy and CT should be used to evaluate patients with neuroblastoma who have undergone BMT.