To investigate the effect of siRNAs specific for T-bet and Eomesodermin (Eomes) in interferon-gamma (IFN-gamma) production of different human T cell subsets.Double-stranded small interfering RNA (siRNA) sequences specific for genes of T-bet and Eomes were chemically synthesized and transfected into anti-CD3 mAb activated alphabeta T cells and Mtb-Ag activated gammadelta T cells. CD4(+), CD8(+) T and gammadelta T cells were sorted by flow cytometry and the expressions of T-bet and Eomes gene mRNA were detected by RT-PCR technique. The changes of IFN-gamma production were determined by flow cytometry.After two series of transfection, the siRNA-FAM(+) cells were about 50% in the transfected cells. The IFN-gamma(+) cells in CD4(+) T cells (50.20%) decreased in the cells transfected with T-bet siRNA (18.46%) but no obvious decrease was observed in the cells transfected with Eomes siRNA, whereas the IFN-gamma(+) cells in CD8(+) T cells (76.51%) decreased in the cells transfected with Eomes siRNA (25.37%) and no obvious decrease was observed in the cells transfected with T-bet siRNA. However, the IFN-gamma producing cells in gammadelta T cells (76.52%) decreased in the cells transfected with T-bet siRNA (56.57%) or with Eomes siRNA (42.53%).At the level of transcription factors, T-bet and Eomes are important transcription factors for the regulation of IFN-gamma production in CD4(+) and CD8(+) T cells, respectively. Both T-bet and Eomes may simultaneously be involved in the regulation of the IFN-gamma production of gammadeltaT cells.