A nationwide retrospective study for the clinical outcomes of 99 patients who had received thymoglobulin at a median total dose of 2.5 mg/kg (range, 0.5-18.5 mg/kg) as a second-line treatment for steroid-resistant acute GvHD was conducted. Of the 92 evaluable patients, improvement (complete or partial response) was observed in 55 patients (60%). Multivariate analysis demonstrated that male sex and grade III and IV acute GvHD were associated with a lower improvement rate, whereas thymoglobulin dose (< 2.0, 2.0-3.9 and ≥ 4.0 mg/kg) was NS. Factors associated with significantly higher nonrelapse mortality included higher patient age (≥ 50 years), grade IV acute GvHD, no improvement of GvHD and higher dose of thymoglobulin (hazard ratio, 2.55; 95% confidence interval, 1.34-4.85; P = 0.004 for 2.0-3.9 mg/kg group and 1.79; 0.91-3.55; P = 0.093 for ≥ 4.0 mg/kg group). Higher dose of thymoglobulin was associated with a higher incidence of bacterial infections, CMV antigenemia and any additional infection. Taken together, low-dose thymoglobulin at a median total dose of 2.5 mg/kg provides a comparable response rate to standard-dose thymoglobulin reported previously, and < 2.0 mg/kg thymoglobulin is recommended in terms of the balance between efficacy and adverse effects.