We evaluated the recovery of human hematopoietic progenitors in long-term bone marrow culture (LTBMC) initiated in tissue culture (TC) flasks to that in "Lifecell" bags, which are gas-permeable plastic bags in which feeder-layer cells cannot adhere. Cells were incubated in presence of IL-1 and IL-3. Our experiments reveal sustained hematopoietic stem cell growth in the absence of a feeder layer in plastic gas-permeable bags. Evaluations of marrow from patients with chronic myelogenous leukemia suggests enrichment of normal hematopoietic precursors. Combining effective drugs to decrease Ph(+) clone prior to bone marrow harvest and use of cultured bone marrow may provide a useful method for treating patients with chronic myelogenous leukemia.