Clinical trials have advanced the cure rate of childhood acute lymphoblastic leukaemia to near 80%. Treatment response, as measured by minimal residual disease, has allowed us to refine risk classification schemes and better tailor the intensity of therapy for each patient. More complete molecular analysis of leukaemia cells, pharmacodynamic and pharmacogenetic studies, and the development of targeted therapy should ultimately lead to further improvements in treatment. Pharmacogenetic studies should allow treatment refinements that will decrease the risk of complications while maintaining high cure rates. In addition, gene expression profiling may improve the genetic classification of leukaemia and identify clinically important subgroups. It may also lead to the identification of new targets for novel antileukaemic agents.