Inclusion Criteria:  Age of the patients between 0 and 17 Diagnosis of hematological or oncological disease undergoing allogeneic bone marrow transplantation Patients undergoing myeloablative conditioning Patients that received ATG as GVHD prophylaxis Patients whose consent has already been acquired for the processing of data for research purposes Minimum follow-up of 12 months  Exclusion Criteria:  Bacterial and / or fungal infection present at the time of bone marrow transplantation Use of Thymoglobulin in the 3 months prior to transplantation Allergy and / or intolerance to the active substances or excipients contained in Thymoglobulin