Results. We found an increased frequency of the HLA-B*40 allele in ALL patients as compared to the control group (14.5% versus 9.84%, P = 0.003, OR = 1.67); this was particularly evident in a subgroup of young (less than 18 years old) ALL patients (P = 0.002, OR = 1.76); likewise, a decreased frequency of HLA-B*40 allele in AML patients was observed as compared to the control group (4.70% versus 9.84%, P = 0.02, OR = 0.42). This evidence concerns the gene HLA-B and acute myeloid leukemia.