Anti-T lymphocyte globulin (ATG) is commonly used as prophylaxis for graft-versus-host disease (GVHD), especially in patients who are at high risk of GVHD. The appropriate dosage of ATG in Japan has not yet been assessed. We therefore conducted a nationwide survey of patients who received ATG-Fresenius as GVHD prophylaxis for unrelated bone marrow transplantation (uBMT). A total of 86 patients were identified (median age 31 years, range 1-68). The median total dose of ATG was 10 mg/kg. The cumulative incidence of neutrophil engraftment was 90 %. The probability of 2-year overall survival (OS) was 67 %. The cumulative incidence of 2-year non-relapse mortality was 25 %. The incidences of grade II-IV and grade III-IV acute GVHD were 20 and 8 %, respectively. The incidences of chronic and extensive chronic GVHD were 19 and 8 %, respectively. In adult patients, there was a reduction of acute GVHD with high-dose ATG (>10 mg/kg), which did not reach statistical significance. In conclusion, the addition of low-dose ATG to GVHD prophylaxis in Japanese patients who received uBMT resulted in decreased incidences of both acute and chronic GVHD without compromising OS. The effects of low-dose ATG should be assessed in a prospective clinical trial.