This publication brings together a number of papers presented at the Fourth Symposium on Clinical Oncology held at the Royal College of Radiologists, London, in February 1982. The subject of the meeting was paediatric oncology, and its objective was to provide an up-to-date review of the management of children with leukaemia and the more common forms of childhood cancer. Cancer in childhood is fortunately uncommon. The descriptive sta­ tistics of these diseases in the United Kingdom, and in many other countries from which data are available, are presented in some detail. Some remarkable differences in the incidence of the leukaemias, for example, are recorded throughout the world. Further studies of the reasons for such differences hopefully may provide some insight into the causation of these diseases. The leukaemias represent the most common form of neoplasia recor­ ded in the Manchester Children's Tumour"Registry, accounting for almost one third of all childhood cancers. Acute lymphoblastic leukaemia is the most common type of leukaemia in children in all countries for which we have adequate data, with the exception of Japan. A masterful review of the achievements in the management of acute lymphoblastic leukaemia is given by Professor R. M. Hardisty.