The cure of childhood acute lymphoblastic leukemia (ALL) was a momentous achievement in the history of medicine. It demonstrated that widely disseminated cancers can be eradicated with cytotoxic drugs, and it illustrated the power of systematic laboratory studies and randomized clinical trials applied to a single disease. As ALL cure rates edge towards 80%, several key challenges are apparent. First, it will be important to devise more effective therapies for the high-risk patients who continue to relapse on contemporary protocols. Second, better methods of disease assessment and treatment are needed to avoid relapses that still occur in so-called low- and intermediate-risk groups. Third, the persistence of late adverse effects due to radiation and certain genotoxic agents, such as the anthracycline compounds and the epipodophyllotoxins, mandates the development of alternative therapies that are both safe and effective in children. The International Childhood ALL Workshop, held 3-4 December 1997, at St Jude Children's Research Hospital in Memphis, Tennessee, brought together leading experts in leukemia therapy to discuss progress in meeting these and other challenges, and to suggest directions for future studies. The participants, from 12 co-operative study groups and two individual centers, were welcomed by Dr A Nienhuis (St Jude Director), who provided the historical context for the workshop, and by Drs W Evans and C-H Pui, the meeting co-organizers.