To assess the relationship between serum concentrations of proinflammatory cytokines and prognosis of non small cell lung cancer (NSCLC), we evaluated the serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1-beta) and interleukin-6 (IL-6) in 60 patients with untreated advanced NSCLC. Mean cytokines concentrations in patients were significantly higher than in the control population. Patients with metastatic disease had higher levels than those with undisseminated disease. Finally, in patients with tumor progression we observed an increase of cytokines serum levels. These results suggest that in NSCLC elevated serum levels of proinflammatory cytokines may have prognostic value being associated with a worse prognosis.