Brain tumors developed in two children after they had received cranial irradiation as central nervous system therapy for acute lymphoblastic leukemia. A review of the literature demonstrated an increased incidence of brain tumors in survivors of acute lymphoblastic leukemia who received central nervous system irradiation. Most of the brain tumors occurred within a decade after radiotherapy. Further data will be required to determine whether early post-radiation brain tumors in patients with acute lymphoblastic leukemia are due to the central nervous system irradiation or to a genetic predisposition.