Between 1980 and 1987, 59 children with acute lymphoblastic leukemia (ALL) or stage IV neuroblastoma (NB) underwent allogeneic or autologous bone marrow transplantation (BMT). Thirty-nine of these patients were alive and in remission 6 months post BMT and were evaluable for this analysis. Sixteen have developed renal dysfunction. Eight were transplanted for relapsed ALL and received an autologous transplant. Preparation included tenopiside (VM 26), cytosine arabinoside, and cyclophosphamide followed by total body irradiation (TBI). One patient received 850 cGy in a single fraction, while all other patients received fractionated TBI (1200-1400 cGy in 6-8 fractions over 3-4 days). Eight of 11 evaluable patients who received a BMT for NB have developed late renal problems (4-7 months after BMT). The preparation for neuroblastoma patients included VM 26, cis-platinum, melphalan, cyclophosphamide and fractionated TBI (1200-1296 cGy). All 8 neuroblastoma patients had received cis-platinum as induction treatment prior to transplantation. All patients presented with anemia, hematuria and elevations of BUN and creatinine. Renal biopsies were consistent with radiation nephropathy. In conclusion, a high incidence of renal dysfunction has occurred after BMT in children with neuroblastoma and ALL. The clinical and laboratory features are consistent with either radiation nephropathy or hemolytic-uremic syndrome. The relatively young age of these patients and conditioning with intensive multi-agent chemotherapy may decrease the tolerance of the kidney to radiation injury.