This review charts the evolution of therapy for childhood acute lymphoblastic leukaemia (ALL) in the United Kingdom. The present chemotherapeutic regimen is the result of experience gained from carefully planned randomised cooperative studies carried out during the last two decades. In common with the experience of the West German and American groups, the best results have been in those treated with post remission intensification blocks. With current chemotherapy protocols, almost 70% of children with ALL in U.K. can be cured but there may be a medical cost of such a cure, in terms of both acute and long term toxicity. This was especially true when central nervous system (CNS) therapy with cranial irradiation was used. Therefore present regimens are examining chemotherapeutic options for CNS disease control and the efficacy of additional post remission intensification. Failure of chemotherapy is most often seen in those children with a presenting white cell count of more than 50 x 10(9)/l, very young children and/or the presence of certain chromosomal rearrangements (e.g. t4: 11, t9: 22). At present the optimum therapeutic option for such high risk patients and for the majority of those in second remission, is an allogenic bone marrow transplant if an HLA-matched sibling is available. Modern day therapy is both complicated and costly and will be beyond the resources available for most children with ALL in developing countries. A significant decrease in worldwide mortality due to ALL will only occur if either the disease can be prevented or a simpler cure devised.