Recent studies have evaluated the cytokine network involved in the local immune response to tumors. In addition to infiltrating inflammatory cells, tumors also produce cytokines and growth factors that may alter tumor growth and tumor immunogenicity. Ninety-one samples of NSCLC were used in this study. We measured the expression of VEGF, TNF-alpha, TGF-beta, IL-6, IL-8, IL-12, INF-gamma, and MCP-1 in NSCLC tissues, by ELISA. The expression of IL-6 and IL-8 were significantly higher in squamous cell carcinoma than in adenocarcinoma (p=0.016 and p<0.001, respectively). The expression of TGF-beta, MCP-1 and IL-8 were significantly higher in pulmonary metastasis positive than negative cases (p=0.002, p=0.001, and p=0.008, respectively). In multivariate logistic regression analysis, the expression of TGF-beta was an independent risk factor for the occurrence of pulmonary metastasis (p=0.008, 95% CI=1.002-1.011). We confirmed that tumor infiltrating stromal cells were major sources of TGF-beta by immunohistochemical analysis. The expression of VEGF and IL-8 were significantly higher in cases with central necrosis (p=0.006 and p=0.011, respectively). We speculated that TGF-beta expression in tumor infiltrating stromal cells may regulate the occurrence of spontaneous pulmonary metastasis in NSCLC. (Ann Thorac Cardiovasc Surg 2003; 9: 295-300)