Herein, we hypothesized the impact of <i>KIR</i> alleles in the <i>KIR A</i> haplotype and cognate human leukocyte antigen (HLA) ligand on leukemia.<h4>Methods</h4>The study cohort included 318 ALL patients, 336 AML patients, and 306 unrelated healthy controls. This evidence concerns the gene KIR3DL1 and leukemia.