Introduction: Hematopoietic stem cells are always in a quiescence state. Since they need retroviral transduction to infect dividing cells, they are resistant to retrovirus transduction. They need to be pre-stimulated by a cytokine cocktail. For proliferation without maturation, we suggest MIP-1a as a novel factor. Material and methods: Retroviral vector produced by PG13/LN C8 cells titter on Hela cells. Then, the CD34+ cells of cord blood can be pre-stimulated in a serum- free media supplemented with SCF, Flt3,TPO,IL6 in the presence and absence of 50 ng/ml MIP-1a. Transduction efficiency was assessed by a semi-quantitative PCR for the neomycin gene.Results: A PCR analysis of the neomycin gene in CD34+ cells revealed an improved transduction of cord blood cells in the presence of MIP-1a 65%, in comparison to its absence: 40.7%.Conclusion: the addition of MIP-1a to the cytokine cocktail improves the transduction efficiency of cord blood hematopoietic progenitor cells. Further studies are required to clarify its effect on the functional properties of CD34+ cells.