Mesenchymal stem cells （MSCs） have many function, including immunomodulatory activity, tissuerepair capability and regeneration of bone, cartilage and fatty tisssues. MSC culture methods have been established, and safety can be ensured, so MSCs have been applied clinically to treatment of numerous diseases. With respect to hematological diseases, MSC treatment is expected to be effective for therapy-resistant acute graft-versus-host disease （GVHD）. In addition, MSCs have been applied to areas such as treatment of chronic GVHD, prevention of GVHD, promotion of hematopoietic stem cell engraftment, and treatment of refractory aplastic anemia. However, on the basis of the cellular characteristics of MSCs, the potential for problems such as increase in relapse, exacerbation of infection, and cancer development must be borne in mind. This article review the current status of, issues with clinical applications to hematological diseases of MSCs.