The selective uptake and accumulation of 131J-Metaiodobenzylguanidine in neuroblastoma cells in vivo may be utilized for targeted irradiation. The experience with 32 neuroblastoma patients refractory to conventional high dose chemotherapy is reported. At diagnosis 8 patients had Evans stage III and 22 stage IV. 11/32 experienced recurrences after complete tumor disappearance and before mIBG treatment, 16/32 progressed from residual or nonresponding tumor and in 3/32 insufficient tumor regression by chemotherapy was observed. 2 children received one mIBG course each with no evidence of disease. Mean applied activity was 128 mCi per course (35-300 mCi), 360 mCi per patient (80-1033 mCi) and 19.2 mCi/kg per patient (3.2-37.9 mCi/kg), respectively. A total of 84 courses was given (mean 2.6 per patient). Pain relief was noticed in 14/14 patients with bone pain. Complete or very good partial remission was achieved in 5/32, partial remission in 11/32 and stable disease in 6/32 patients. In 8 children progression occurred and 2 patients were not evoluable. 20 children died, 12 are still alive (6 patients with initial stage IV, 6 with stage III disease). Main side effect was transient thrombocytopenia, which became more severe with increasing number of courses. We conclude that mIBG treatment is effective in some patients with refractory neuroblastoma and may be utilized in the future as front line therapy for patients achieving only incomplete regressions after high dose chemotherapy.