Objective: To investigate the role of cytokines IL-2, IL-4, IL-10, IL-12, and IFN-γ in pathogenesis of acute graft-versus-host disease (aGVHD) after allogeneic peripheral blood stem cell transplantation (allo-PBSCT). Methods: Forty-two patients undergoing allo-PBSCT were included in this study. Reverse-transcriptase polymerase chain reaction(RT-PCR) was used to analyze gene expression of cytokines IL-2, IL-4, IL-10, IL-12, and IFN-γ. Results: All patients achieved engraftment, 18 patients developed grade Ⅰ GVHD, 6 patients developed grade Ⅱ - Ⅳ GVHD. The gene expression of IL-2, IL-12, and IFN-γ increased, the gene expression of IL-4 and IL-10 decreased. Conclusion: Cytokines IL-2,IL-12, and IFN-γ lead to a positive regulation of the development in human aGVHD, and IL-4 and IL-10 play negative regulatory roles.