PURPOSE: There is mounting evidence demonstrating that stromal cell derived factor-1 (SDF-1) plays an important role in homing of hematopoietic progenitor cells to bone marrow. This study was aimed to assess whether bone marrow mesenchymal stem cells overexpressing exogenous SDF-1 could synergistically promote the homing of CD34(+) (Cluster of Differentiation [CD]) cells to bone marrow of lethally irradiated severe combined immunodeficiency (SCID) mice. METHODS: Human SDF-1 complementary Deoxyribonucleic acid (cDNA) was transfected into bone marrow-derived mesenchymal stem cells with recombinant lentiviral vector. The expression of SDF-1 was detected by real-time Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA), and the ex vivo chemotaxis function on CD34(+) cells was measured by coculture system and Transwell system. SDF-1 gene-modified mesenchymal stem cell (MSC) and CD34(+) cells were infused into lethally irradiated SCID mice and the hematopoietic reconstitution in the recipient mice was examined. RESULTS: Messenger ribonucleic acid (mRNA) and protein of SDF-1 in infected MSC were significantly higher than that of the non-infected control MSC (p < 0.05). The infected MSC have significant chemotaxis effect on CD34(+) cells in vitro and promote hematopoietic reconstitution after CD34(+) cell transplantation in vivo. CONCLUSION: MSC with high-level expression of SDF-1 can synergistically promote hematopoietic reconstitution after CD34(+) cell transplantation in lethally irradiated SCID mice.