Objectives: We aimed to evaluate the safety of total body irradiation before bone marrow transplant. Materials and Methods: We analyzed 110 patients (65 male, 45 female) who underwent total body irradiation for hematopoietic stem cell transplant between May 1998 and March 2013. Median age at total body irradiation was 17 years (range, 1-62 y). Median observation time was 777 days (range, 31-5494 d). Initial diagnoses were acute lymphoblastic leukemia (24 patients), acute myeloid leukemia (26 patients), chronic myeloid leukemia (7 patients), myelodysplastic syndrome (8 patients), malignant lymphoma (13 patients), mucopolysaccharidosis (12 patients), neuroblastoma (10 patients), and other diseases (10 patients). The total fractionated dose used for total body irradiation was 12 Gy in 69 patients and 6.0-10.8 Gy in 29 patients. Single-dose total body irradiation was administered to 12 patients. Most patients (63 of 110) received chemotherapy consisting of cyclo phosphamide alone. Results: Ocular complications were observed in 29.5% of the patients. Hypothyroidism, interstitial pneumonia, obliterative bronchiolitis, and veno-occlusive disease developed in 8.2%, 1.8%, 0.9%, and 2.7% of patients. Growth abnormality was observed in 10 (20%) of the 50 pediatric patients. The use of a lower dose (< 12 Gy vs 12 Gy) of fractionated total body irradiation did not decrease the incidence of adverse events; however, nonmyeloablative conditioning with low-dose single-fraction total body irradiation reduced the incidence of adverse events. Three patients who underwent total body irradiation as reirradiation therapy achieved long-term survival without adverse events. Conclusions: Fractionated total body irradiation given at a lower dose (< 12 Gy vs 12 Gy) did not decrease the incidence of adverse events.