Despite prophylactic measures, susceptibility to severe infections in patients who had undergone bone marrow transplantation (BMT) is quite variable. To evaluate the potential role of human leukocyte antigen (HLA)-E polymorphism on the incidence of early infections, we analyzed 77 unrelated-donor (UD) BMT pairs identically matched for classical HLA class I and class II alleles. Multivariate analysis taking into account the patient-, donor- and transplant-related factors showed that bacterial infections and transplant-related mortality (TRM) at day 180 were high when the donor genotype was HLA-E*0101/E*0101 (hazard ratio [HR]=2.20; P=0.03 and HR=2.12, P=0.048, respectively), suggesting that homozygous state for HLA-E*0101 allele is a risk factor for early severe bacterial infections and TRM in UD-BMT.