The purpose of this study was to evaluate the prognostic significance of programmed cell death-ligand 1(PD-L1)expression and CD8+T cells in the immune microenvironment. From January 2011 to December 2011, we retrospectively examined 31patients with Stage III colorectal cancer. PD-L1expression and CD8+T cell counts were evaluated by immunohistochemical study using whole-tumor slides. PD-L1expression in cancer cells(PDCC)and in tumor-infiltrating stromal cells(PDSC)was divided into high(H)and low(L)groups. CD8+T cells were counted in the core of the tumor(CDCT)and in the invasive margin of the tumor area(CDIM), and divided into high(H)and low(L)groups. Based on a median follow-up time of 69.3 months, the 5-year overall survival and disease-free survival of all patients were 74.2% and 64.5%, respectively. The overall survival was significantly longer for patients in the CDIM-H group(82.6%)than those in the CDIM-L group(50.0%; p= 0.034). Patients in the PDSC-H group also tended to have superior overall survival than those in the PDSC-L group(84.2% and 58.3%, respectively, p=0.094). In conclusion, both CD8+T cells and tumor-infiltrating immune cells with PD-L1may indicate antitumoral function in patients with Stage III colorectal cancer.