Patients Patients receiving an allotransplant at participating hospitals during the study period before initiating conditioning period.  Inclusion Criteria:  Patients of any age who will receive allogeneic hematopoietic transplantation of any modality with any diagnosis. Agreement of the patient to participate by signing the informed consent or his/her legal representatives/assent (if applicable).  Exclusion Criteria  - Allotransplant recipients in stages after the initial pre-conditioning.  Donors  Family donors from patients included in the study:  Inclusion criteria:  Agreement of the donor to participate by signing the informed consent or his/her legal representatives/assent (if applicable). Donor relatives with any degree of identity in the Human Leukocyte Antigens (HLA).  Exclusion Criteria:  Unrelated donors Transplants from umbilical cord blood source.