Background: Although a causal relationship for inflammation and immunity of cancer is more widely accepted today, the precise cell mechanisms mediating this relationship have not been elucidated. Vascular endothelial growth factor (VEGF), previously known as vascular permeability factor. 45 kDa protein, belongs to a family of platelet-derived growth factors. VEGF, inflammation-related protein, could contribute to the accumulation of immunosuppressive cells (MDSC, Treg, TAM, and Tie-2-expressingmonocytes) in tumor-bearing hosts through direct or indirect mechanisms. Methods: We tested the serum levels of VEGF by ELISA in 106 patients including 43 with gastric and 63 with colorectal cancer, and they were increased in advanced stages of gastric and colorectal cancer. Production of IL-17, pro-inflammatory cytokine, with a stimulation of PHA was measured by ELISA and MDSC (myeloid-derived suppressor cells), one of major immunosuppressing cells, was measured by flow cytometry (CD11b+CD14-CD33+). Neutrophil to lymphocyte ratio (NLR) and C-reactive protein (CRP) were used as inflammatory markers. Production of IL-12 and SI (stimulation index) of blastogenic response of lymphocytes were used as markers of cell-mediated immune response. Results: The concentrations of VEGF were positively correlated with levels of MDSC, production of IL-17, NLR and CRP, and were inversely correlated with IL-12 production, SI and nutritional markers including prealbumin and retinol binding protein. The patients were both divided into two groups with a serum level of VEGF (330 pg/ml) and OS (overall survival) of patients with stages III and IV gastric or colorectal cancer were both significantly worse in patients with high levels of VEGF than in those with low VEGF although the differences were not significant in patients with stagesⅠand II. Conclusions: The results of the present study suggested that VEGF may have an impact on advancement and progression involving inflammation and serve as useful markers of the immune suppression involving MDSC, malnutrition and poor prognosis in patients with gastric and colorectal cancer.