Conventional methods of treatment having failed in 17 children (aged 9/12 to 16 5/12 years) with incurable solid malignant tumours underwent whole-body hyperthermia (41.8-42.0 degrees C, for 2-3 h), hyperglycaemia (20-25 mmol/l) and polychemotherapy. Five children had neuroblastoma (stage 4), three Wilm's tumour (stage 4 or 5, unfavourable histology), five skeletal sarcoma with metastases, three inoperable malignant liver tumour, and one brainstem tumour of unknown histology. Whole-body hyperthermia was induced by extracorporeal blood warming in an haemodialysis apparatus under neuroleptic analgesia, thermistors measuring the temperature in the oesophagus, rectum, trachea and skin. There were on average four treatment sessions (between one and ten, total 58), a week apart. The result could be assessed in 12 children: one persisting complete remission (19 months-metastasising renal rhabdoid tumour), eight partial or incomplete remissions, and three nonresponders (osteogenic sarcoma; Ewing sarcoma; brainstem tumour). If the risk can be satisfactorily judged the method is useful and of bearable toxicity. The results point to a high antitumour effectiveness of combined hyperthermia and chemotherapy.