From January 2012, all Italian recipients have been typed with HR-HLA typing at the starting of the unrelated donor search process with a consequent advantage in terms of "non selected population" as object of the present observational trial. Moreover, the larger size of cohort of patients who underwent unrelated HSCT during a smaller study period of 2 years should lead to a more effective analysis including the assessments of permissive and non-permissive I and II class HLA incompatibilities. Finally, in order to give a stronger statistical power to this trial, particular efforts have been drawn in order to recovery data about the graft versus host disease prophylaxis.