Vascular endothelial growth factor (VEGF) is known to play crucial role in tumour angiogenesis. It is demonstrated that VEGF can be up-regulated by oxidative stress. The aim of this study was to determine the serum VEGF levels and oxidative stress in patients with primary lung cancer and to investigate their association with clinicopathologic factors. We measured serum VEGF levels and oxidative stress in 63 patients (age 63.02+/-1.12 S.E.M.) with primary lung cancer before any treatment (39 NSCLC and 24 SCLC; 6 patients stage I, 3 stage II, 25 stage III and 29 stage IV) and 25 normal subjects. The serum VEGF levels were measured with enzyme linked immunosorbent assay. Serum oxidative stress levels were detected by a commercially available assay (D-ROMs test, Diacron, Grossetto, Italy). The levels of oxidative stress in patients were higher than those in normal subjects (555.3+/-30.35 UCarr vs. 360.1+/-17.46 UCarr). Additionally, a significant difference was found in serum VEGF levels between lung cancer patients and healthy control subjects (428.1+/-38.42pg/ml vs. 298.8+/-19.89pg/ml, respectively, p=0.040). Interestingly, serum oxidative stress presented a significant correlation with serum VEGF levels in patients with lung cancer (r=0.542, p=0.002). Serum VEGF levels were significantly associated with the clinical staging (N-stage) of the patients (p=0.023), performance status (p=0.004) and age (p=0.004). In conclusion, oxidative stress and VEGF are significantly increased in patients with primary lung cancer. The correlation between them might implicate new aspects of the mechanisms controlling tumour angiogenesis and may present clinical interest in the future. Further studies are warranted to evaluate the role of oxidative stress and VEGF as possible biomarkers for the diagnosis and follow-up of patients with lung cancer.