<p><b>OBJECTIVE</b>To analyze the factors affecting the prognosis of completely resected nonsmall cell lung cancer (NSCLC), and to assess the impact of vascular invasion and TNM stage on prognosis.</p><p><b>METHODS</b>Between March 1, 1997 and March 1, 2002, a total of 1826 pathologically confirmed NSCLC patients with complete resection were enrolled in this study. The major clinical and pathological features were analyzed, and the impact of vascular invasion on prognosis was investigated. Statistical analysis was performed with SPSS software. Fisher's exact test was used to assess the correlation of vascular invasion with the other clinicopathological variables. Survival was analyzed by Kaplan-Meier method and Cox regression.</p><p><b>RESULTS</b>Of the 1826 patients, 126 were found to have vascular invasion. Univariate analysis revealed that the following factors was significantly correlated with shorter overall survival: family history of cancer, histological type, pathological stage and vascular invasion, whereas multivariate analysis confirmed that only pathological stage and vascular invasion were the significant prognostic factors with a hazard ratio of 2.80 [95% CI 1.74 - 4.86] and 4.76 [95% CI 2.38 - 6.21], respectively. The overall 5-year survival rate of this series was 57.4% for stage I, 34.2% for stage II and 18.7% for stage III (P = 0.001) ,respectively. It was 59.1% for stage I 36.2% for stage II and 20.0% for stage III for those without vascular invasion, whereas for those with vascular invasion, it was 37.5% for stage I, 24.0% for stage II and 7.0% for stage III, respectively. There was a significant difference among the patients with different TNM stage and between the patients with vascular invasion and without (P < 0.05) by log-rank test. The distant metastasis rate of the patients with vascular invasion was 69.9% versus 36.7% in those without (P < 0.001).</p><p><b>CONCLUSION</b>Our results show that TNM stage and vascular invasion are significant prognostic factors in nonsmall cell lung cancer. Vascular invasion can not only serve as an independent prognostic factor, but can also predict the possibility of metastasis.</p>