Improved survival rates in acute childhood leukemia have been associated with an increasing number of complications in the ileocecal region. An experience is reported with 11 children who developed inflammation, perforation, and/or necrosis of the ileum, appendix, and/or cecum (leukemic ileocecal syndrome). The clinicopathologic correlation, roentgenographic findings, and results of treatment are presented. Once the ileocecal complication developed, the prognosis was grave. Surgical intervention was not helpful, regardless of whether the bone marrow was in remission or relapse. The importance of recognizing this entity is emphasized because of its clinical similarity to acute appendicitis.