A new serum-free culture (SFC) system for human AML-CFU was established and the colony-promoting activity of four recombinant human hematopoietic growth factors (rhHGFs) including granulocyte-macrophage colony-stimulating factor (rhGM-CSF), interleukin-3 (rhIL-3), erythropoietin (rhEPO) and newly developed stem cell factor (rhSCF) were investigated in this SFC system. Under the orthogonal design condition, it was found that human AML-CFU presented optimal clonal growth in an environment of bovine serum albumin (0.6 %), saturated human transferrin (2× 10-6 mol/L), cholesterol (2.8 μg/ml), bovine insulin (15 μg/ml), bovine hemin (0. 05 mmol/L), linoleic acid (2. 8 μg/ml), and IMDM. Spontaneously growing colonies were observed in 11 out of14 cases studied. The plating efficiencies obtained by culturing with rhGM-CSF, rhIL-3, and rhSCF were 0. 776±0. 621 %, 0. 574±0. 510 %, and 0. 647±0. 543 % (x±s), respectively. There was one case (M3b) showing no response to all HGFs in both SFC ad SCC. The clonal growth of AML-CFU obtained from peripheral blood of the patient with M6 was unexpectedly marked. As a whole, the newly designed SFC system has been demonstrated to be useful for culture of human AML-CFU from both bone marrow and peripheral blood.