Chimerism is a state in which bone marrow hematopoietic stem cells from two genetically different animals coexist. To date, the approach has been used successfully to induce the state of immunologic tolerance in the animal models and is now being evaluated in clinical trials of both HLA-identical and HLA-mismatched living-donor kidney transplant recipients in some transplant centers with varying degrees of success. Although the results are promising, the current conditioning regimens are not optimal and longer-term follow up and multicenter studies are needed to ensure the efficacy and safety of the procedures.