1,120 children were included in protocol FRALLE 93 from june 1993 to september 1998. Disease Free Survival for the all protocol is 78% +/- 3 and overall survival 83% +/- 3. Various clinical and laboratory features at the time of diagnosis have been correlated with prognosis. They provide a potential mean to stratify patients into treatment subgroups according their relative risk of treatment failure. The identification of these prognostic factors has been an essential element in the design of current therapeutic trials. Prognostic characteristics of childhood ALL include: age, white blood cell count, tumor burden, cytogénétics (chromosome count and chromosomal translocation), immunophenotype and early response to treatment. Molecular biology has been the revolution of the last two decades permitting the cloning of the genes involved in the leukemic process. Finally the new molecular techniques allow a sensitive diagnostic approach to minimal residual disease (MRD). The better detection of MRD must allow a more rational basis for therapeutic intensification for a subset of poor responder patients. A decrease in therapy of very good responders can also be envisaged.