In allogeneic hematopoietic stem cell transplantation (allo-SCT), most physicians in Japan utilize granulocyte colony-stimulating factor (G-CSF) at a high dose (HD) of 300 μg/m(2) per day for filgrastim to promote faster neutrophil engraftment. However, the necessity of the HD has not been validated under graft-versus-host disease (GVHD) prophylaxis by mycophenolate mofetil (MMF), which can also be expected to facilitate engraftment. In a total of 51 patients, we compared the clinical outcomes between a standard dose (SD) fixed at 300 μg per day and a HD of G-CSF. While time to neutrophil engraftment was not different in the HD and SD groups in patients receiving cord blood transplantation (CBT, 20 vs. 17.5 days, P = 0.243) or bone marrow transplantation (BMT, 11 vs. 10 days, P = 0.227), there seemed to be an increased risk of developing acute GVHD in the HD group with CBT (20 vs. 0%, P = 0.073) and BMT (57 vs. 24%, P = 0.165). Progression-free survival of patients in the HD group was likely to be worse compared with that of the SD group with CBT (P = 0.099). In this study, the clinical benefits of a HD of G-CSF could not be documented, and we find that the use of G-CSF at a SD after allo-SCT with MMF should be prospectively evaluated.