Abstract: Objective To study the efficacy of combined use of low-dose granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in mobilizing hematopoietic stem/progenitor cells. Methods Twenty adult patients with malignant hematologic diseases were paired using statistical methods, and the 10 pairs were divided into 2 equal groups. For non-Hodgkin lymphoma, the treatment regimen adopted intravenous infusion of cytoxan (2 g/d for 1 or 2 d) and VP16 (0.2 g/d for 1 to 3 d), while for acute non-lymphocytic leukemia, Ara-C (2 g/d for 1 to 3 d) and VP16 (0.2 g/d for 1 to3 d) were used. When the while blood cell count (WBC) was below 1.0×10⁹/L, G-CSF and GM-CSF were administered subcutaneously at the same dose of 2.5 μg/d·kg in the 10 patients in the experimental group, while the patients in the control group received only 5 μg/d·kg G-CSF, both for 5 to 6 d. After WBC>5.0×10⁹/L, the peripheral blood mononuclear cells (PBMNC) were separated by CS-3000 pluse separator and CD34⁺ cells were determined by flow cytometry. Results The purity of the isolated PBMNC was 95%-99%. In the experimental group, the mean number of CD34⁺ cells acquired was 9.4×10⁶/kg ranging from 8.4×10⁶ to 10.2×10⁶/kg, and granulocyte-macrophage colony-forming unit (CFU-GM) was 42.4×10⁴/kg on average ranging from 21.9×10⁴ to 72.8×10⁴/kg, as compared with 4.8×10⁶/kg[(4.1-8.3) ×10⁶/kg]for CD34⁺ cells and 28.1×10⁴/kg[(7.1-60.2)×10⁴/kg]for CFU-GM in the control group (P<0.05). No obvious difference was observed between the two groups in terms of the adverse effects of the treatment (P>0.05). Conclusion Combined use of G-CSF and GM-CSF can be more effective than the exclusive use of GM-CSF for mobilizing CD34⁺ cells.