Survival of 873 acute lymphocytic leukemia patients has been reviewed in relation to a number of patient and disease characteristics at first hospital admission. Study of survival by individual years of age at diagnosis led to the selection of five age intervals: 1-3, 4-10, 11-19, 20-49, and 50 years and over. For each sex the survival after age 10 was considerably poorer than for the younger ages. The best survival for any age-sex group was that for girls 4-10, who had a median survival time of 14.0 months compared with an overall median survival time of 7.8 months for patients of both sexes over 1 year of age. We attempted to determine whether a favorable distribution of other factors related to survival might work to the advantage of girls in the 4-10 year age group. However, in studying factors such as symptoms and hematological characteristics it was the pattern, rather than the exception, to find within most levels of a characteristic under study, that girls 4-10 had the best survival. It would be interesting and potentially valuable to see whether the findings in this study are confirmed in other series. If a specific age-sex group tends to maintain a superior survival pattern, additional exploration of prognostic factors may uncover important leads concerning the biology of the disease.