The inventors have discovered that hematologic disorders, e.g., both neoplastic (hematologic cancers) and non-neoplastic conditions, can be treated by the induction of mixed chimerism using myeloreductive, but not myeloablative, conditioning. Methods of the invention reduce GVHD, especially GVHD associated with mismatched allogeneic or xenogeneic donor tissue, yet provide, for example, significant graft-versus-leukemia (GVL) effect and the like.