Neuroblastoma (NB), a childhood radiosensitive tumor, is very aggressive and malignant; in its disseminated form, despite very intensive chemotherapy, prognosis continues to be dismal. Owing to its capacity to concentrate in NE lesions, large doses of 131-I-MIBG, have given very encouraging therapeutic results in patients resistant to conventional therapy as well as at diagnosis. We recently reported the first attempt in combination therapy (CO-TH) using 131-I-MIBG and cisplatin. This new form of CO-TH appears very effective in obtaining a rapid and excellent response in relapsed patients. In this report, we describe the results of further experience with CO-TH in disseminated NE. We have attempted to verify to what extent interaction between the effects of the two agents may produce therapeutic benefit, and we have sought the optimization of CO-TH use. Three stage IV NE patients were treated with CO-TH. The following treatment schedule, was planned: day 1, cisplatin 50 mg/m(2) i.v. over 6 h; day 2, 131-I-MIBG 100-130 mCi at high specific activity (-1.1 Gbq/mg) i.v. over 6 h followed, a week later, by the same treatment combination. The therapeutic results were encouraging. However, hematological toxicity continued to represent a major limiting factor. In view of the overall effectiveness of CO-TH, at the price of lasting hematological toxicity, it may be indicated as a consolidation regimen some time before conditioning chemotherapy for autologous bone marrow transplantation.