To investigate the influence of G-CSF mobilization on functions of donor T lymphocyte subpopulation and acute graft-versus-host disease, peripheral blood samples of 20 healthy donors were collected before and after G-CSF mobilization. The whole blood was diluted with IMDM in ratio of 1:1 and then incubated with PMA + ionomycin + monensin at 37 degrees C, 5% CO2 for 4 hours. After being mobilized and stained, the IL-4, IFN-gamma and IL-2 positive cells were counted with three-color flow cytometry. The results showed that before G-CSF mobilization, the percentages of donor's CD3(+)IFN-gamma(+), CD4(+)IFN-gamma(+), CD8(+)IFN-gamma(+) T cells were 3.2% (0% - 45.9%), 1.3% (0% - 23.8%) and 1.5% (0% - 22.2%) respectively. The percentage of above mentioned cells in donor increased to 19.2% (0% - 53.9%), 9.5% (0% - 49.5%), 7.5% (0% - 38.1%) respectively after G-CSF mobilization. The IL-2 positive CD3(+), CD4(+) and CD8(+) T cell percentage in pre-G-CSF mobilized donors was 1.5% (0% - 31%), 0.8% (0% - 30.0%) and 0% (0% - 5.3%) respectively and subsequently increased to 25.7% (0% - 51%), 19.8% (0% - 39.7%), 4.6% (0% - 20.9%) respectively after G-CSF mobilization. The IL-4 positive T subpopulation did not increased significantly after G-CSF mobilization. In the early stage after peripheral blood stem cell transplantation, donor's Tc1 percentage in aGVHD group was significantly higher than that in non-aGVHD group. The morbidity of severe aGVHD in high Tc2 percentage group was significantly lower than that in low Tc2 percentage group. It is concluded that the donor's type I T cells increase after G-CSF mobilization, the Tc1 percentage of G-CSF mobilized donor is correlated with the occurrence of aGVHD in the early stage after HSCT, the percentage of Tc2 in donor is negatively correlated with aGVHD morbidity in recipients.