The identification of important prognostic factors at diagnosis of childhood leukemia has been very useful in explaining the marked differences in disease outcome. After a complete remission is achieved, it is interesting to determine whether the ability to maintain a complete remission and the patient's survival continue to be influenced by the prognostic factors identified at diagnosis. If the maintenance of complete remission and survival continue to be influenced, it is important to determine the magnitude of this effect and its variations with time. Data from a study population of 936 children with newly diagnosed acute lymphoblastic leukemia were analyzed to determine the duration of effect for three variables showing strong prognostic influence: WBC, age at diagnosis, and sex. The strongest of these, WBC, showed a gradual attenuation of effect for children in progressively longer periods of complete continuous remission to a virtual disappearance at 24 months. Age and sex showed a similar reduction in prognostic effect with a negligible contribution at 15 months of continuous complete remission. However, sex becomes an important variables again with a late effect on recurrence results in patients who experience long periods of remission.