Purpose:To investigate the relationship between involved extent of lymph node parenchyma and prognosis of patients with stageⅢ non-small-cell lung cancer (NSCLC) and define the appropriate surgical indications for the patients. Methods:From 1988 to 1998,one hundred and sixteen patients with NSCLC underwent systematic lymph node dissection and were diagnosed to have metastasis in mediastinal lymph node (N_(2) disease), whose clinical data were reviewed. According to the clinical and pathologic characteristics of the involved mediastinal lymph node, the patients were divided into subgroups. Survival rates were calculated and survival curves were prepared by Kaplan-Meier method. Survival differences among the subgroups were compared by Log-Rank test. Results:Involved extent of lymph node parenchyma had an important effect on the prognosis. In N_(2) disease with extra-capsular metastasis and intact capsule, 5-year survival rates were 9.8% and 18.8%, respectively. The survival difference between extra-capsular metastasis subgroup and inner-capsular metastasis subgroup was of statistical significance (P