In Japan, where living donor kidney transplants account for approximately 85% of all cases, ABO-incompatible transplants are commonly performed. These procedures carry a risk of humoral rejection due to antibody–antigen reactions against ABO blood group antigens expressed on graft vascular endothelium, in addition to the usual cellular immune responses. As a result, specific perioperative management is required. Immunosuppressive advances have made graft survival in ABO-incompatible transplants comparable to compatible ones (Fig. 39.1).