Cytokines mediate numerous physiological and immune reactions, which are manifested in various biological effects, including tumouricidal activity. We evaluated the expression of the pleiotropic cytokine, tumour necrosis factor-alpha (TNF-alpha), by competitive PCR technique in 47 non-small cell lung cancer (NSCLC) cases and the impact of TNF-alpha on their clinical behaviour. Using univariate analysis, our study demonstrated a positive correlation between high TNF-alpha expression and favourable prognosis in NSCLC in terms of overall survival and disease free interval (p=0.03 and 0.04, respectively) and TNF-alpha maintained its independent role in multivariate analysis. TNF-alpha can stimulate the expression of many molecules, including interleukin-8 (IL-8) and endothelin-1 (ET-1); in our study, the expression of TNF-alpha was significantly associated with high IL-8 mRNA levels (p=0.008) and ET-1 mRNA positivity (p=0.03). We suggested that TNF-alpha can induce ET-1 mRNA expression in NSCLC, similarly to IL-8 expression. Our study may also contribute to advancing the knowledge of the molecular relationship between cytokines and endothelial functions in NSCLC.