In this symposium, a new concept, alloreactive NK cells regulated by KIR, was discussed extensively. There is no doubt that KIR epitope compatibility has a critical impact on the transplantation outcome; however, it is too early to determine the significance of KIR genotyping over KIR epitope assumption based on HLA type. We need to wait for a large-scale analysis to be done before we know the answer. What became clear in this meeting is that big collaborations or multicenter studies are becoming more important as sources of ethnic background data, and many other factors are found to affect clinical outcomes, making center-to-center comparisons more difficult.