To elucidate the feasibility of retroviral mediatedtransfer of multidrug resistance gene (mdrl) intohematopoietic stem/progenitor cells, the CD34~+ cellswere isolated from bone marrow by using a high-gradient.magnetic cell sorting system, and the efficiency ofretroviral mediated gene transfer was studied. Materials To elucidate the feasibility of retroviral mediated transfer of multidrug resistance gene (mdrl) into hematopoietic stem / progenitor cells, the CD34 ~ + cellswere isolated from bone marrow by using a high-gradient. Magnetic cell sorting system, and the efficiency of retroviral mediated gene transfer was studied Materials