The effects of GM-/G-CSF and darbepoetin-alpha on stem cell mobilization were investigated. From February 2005 to March 2007, 30 allogeneic sibling donors were randomly assigned to a G-CSF group (5 microg/kg/day for 5-7 days) or triple group (GM-CSF 10 microg/kg/day on 1st and 2nd day, G-CSF 5 microg/kg/day for 5-7 days, and darbepoetin-alpha 40 mg on 1st day). The MNCs and CD34(+) cells were not different between the two groups, although the doses (x10(8)/kg of recipient body weight) of CD3(+) cells (3.64 +/- 1.75 vs. 2.63 +/- 1.36, P = 0.089) and CD8(+) cells (1.07 +/- 0.53 vs. 0.60 +/- 0.30, P = 0.006) were lower in the triple group. The engraftments, frequency of RBC transfusions, and hemoglobin recovery were not different between the two groups. The cumulative incidence of overall and Grades II-IV aGVHD was 64.3% vs. 61.1% and 25.9% vs. 27.1% in the G-CSF and triple regimen group, respectively, whereas the cumulative incidence of cGVHD was 20.8 +/- 1.3% and 24.4 +/- 1.7%, respectively. In conclusion, the triple regimen did not seem to be superior to G-CSF alone in terms of the CD34+ cell dose, hemoglobin recovery, and GVHD. However, the CD8+ cell count was significantly lower in the triple regimen group. The role of a lower CD8+ cell count in the graft may need to be elucidated in the future.