Ten patients with neuroblastoma were scintigraphed with I131-meta-iodobenzylguanidine (MIBG). Lugol solution was previously administered orally to all patients in order to avoid uptake of radioactive iodide by the thyroid gland. The compound was injected intravenously, 0.5 mCi/1.73 m2 of body surface. Scintigraphy was performed at 24, 48 and 72 hours and 6-7 days after administration of the radioactive preparation. Positive radiotracer uptake was demonstrated in all primitive tumors and metastases, showing a positivity of 100%. MIBG has proven to be the most useful technique in defining the stage of the disease. Mechanism of the tumoral uptake in relationship to catecholamine metabolism is discussed. Differences observed in MIBG radioactivity seen in the urinary bladder, heart and liver in children with or without. Neuroblastoma are discussed. MIBG has also been useful in the follow-up of patients with neuroblastoma.