The seventh annual multidisciplinary symposium on clinical oncology organised by the Royal College of Radiologists discussed the subject of malignant brain tumours. It was held in London in February 1985 and this volume collects together the edited texts of the papers which were presented at the meeting. Primary tumours of the central nervous system account for about 9070 of all malignant diseases but as much as 20% of all paediatric neoplasms. The prognosis ranges from excellent for some of the less aggressive tumours, through good for children's tumours such as medulloblastoma, to appalling for the high-grade adult astrocytomas. Improvements in pathological diagnosis and surgical and radiothera­ peutic techniques have led to considerable sequential improvements in outcome over those obtained in the past. In contrast the response to chemotherapy over the whole range of tumours remains disappoint­ ing, and clearly awaits new drugs and methods of delivery. The relative rarity of individual types of tumours, apart from the commoner high-grade adult astrocytomas, has made progress in terms of clinical trials difficult to organise. In spite of this much investigative work is in progress. The symposium, and the present volume, were designed to provide a comprehensive overview of the subject by experts, with an emphasis on the possible routes to future progress. The topics included aspects of pathology, imaging, diagno­ sis and treatment of both the common and uncommon primary tumours. It is hoped the papers will stimulate further interest and activity in this difficult area of clinical therapy and investigation.