The use of DLI can change chimerism and prevent rejection and relapse. However, the prerequisite for a successful use of this powerful and potentially harmful tool is a minimal burden with resting leukemia or in the case of nonmalignant disease autologous cells. Therefore, a monitoring of the hematopoietic chimerism and of the post-transplant MRD is recommended with a narrow (best: weekly) time schedule. Also, using low and increasing numbers of DLI, a GvHD can be avoided or even minimized.