One recent line of cancer research shows increasing interest for biological factor such as IL-2, TNF-alpha, and leptin, which have been found to participate in the development and progression of non-small cell lung cancer (NSCLC). The aim of this study was to measure IL-2, TNF-alpha, and leptin concentrations in the airways and in the systemic circle of patients with NSCLC, investigating the role of these factors in the lung tumors. We enrolled 32 patients (17 men, 71 +/- 7 years) with a histological diagnosis of NSCLC and 20 healthy ex-smoker controls, negative for computed tomography of the chest (14 men, 69 +/- 8 years). IL-2, TNF-alpha, and leptin levels were measured in the serum, the urine, the bronchoalveolar lavage, the induced sputum, and exhaled breath condensate (EBC) of patients enrolled by means of a specific enzyme immunoassay kit. Higher concentrations of IL-2, TNF-alpha and leptin were found in NSCLC patients than in controls (p < 0.0001). A statistically significant increase of IL-2, TNF-alpha, and leptin concentrations was observed in patients from stage I to stage III of NSCLC. These findings suggest that IL-2, TNF-alpha, and the leptin play an important role in the cancerogenesis of NSCLC. Their measure in the EBC could be proposed as noninvasive markers for an early detection of NSCLC and in the follow-up of this tumor.