This is a review of the progress achieved in the treatment of acute lymphoblastic leukaemia, based on a series of 1580 children treated in Prof. Jean Bernard's unit, Paris, from 1956 to 1976. The children are retrospectively divided into three prognostic classes and five therapeutic categories. The benefits obtained from successive additions to the therapeutic armentarium during that period are conspicuous in all classes and categories and particularly striking in children with poor initial prognosis. The role of each component of the therapeutic measures applied is discussed.