Transplantation using donors with KIR B haplotypes leads to less relapse and TRM, and equivalent acute GVHD, but increased chronic GVHD. The cumulative incidences of relapse, TRM, acute GVHD, and chronic GVHD are shown for transplantation using donors with (KIR B/x) or without KIR B (KIR A/A) haplotypes. The incidence of chronic GVHD was higher using KIR B/x donors (39% [95% CI: 34-45]) than when using KIR A/A donors (28% [95% CI: 20-35], P = .02). Acute GHVD, relapse, and TRM were not significantly different between donor KIR haplotype groups (P > .15).