Iodine-131-3F8, a murine IgG3 monoclonal antibody specific for ganglioside GD2 was evaluated by radioimmunoscintigraphy in 42 patients with neuroblastoma. Comparison was made with 131I-metaiodobenzylguanidine (MIBG), 99mTc-methylene diphosphonate (MDP) bone scans, as well as computed axial tomography (CT) or magnetic resonance imaging (MRI). Iodine-131-3F8 detected more abnormal sites (283) than [131I] MIBG (138) or 99mTc-MDP (69), especially in patients with extensive disease. In 20 patients with soft-tissue tumors demonstrated by CT/MRI, 131I-3F8 detected the disease in 18. Upon surgical resection, two tumors interpreted as negative with 131I-3F8 imaging revealed ganglioneuroma, one showing microscopic foci of neuroblastoma. In contrast, 131I-3F8 imaging identified tumors that were confirmed histologically as neuroblastomas. In 26 patients with evidence of marrow disease by antibody scans, 14/26 had confirmation by iliac crest marrow aspirate/biopsy examinations. We conclude that 131I-3F8 scintigraphy has clinical utility in the management of patients with neuroblastoma by improving the sensitivity of tumor detection.