A series of cases of lung cancer were analyzed, with particular attention to the relationship between the presence of lymph node metastases and the prognosis for surgical intervention. The cases are classified into four clinical stages and a detailed classification of histologically proved lymph node metastasis and pleural involvement is presented. Results indicate that the presence of mediastinal lymph node metastasis, especially in cases with squamous-cell carcinoma and negative subcarinal lymph node, does not contraindicate surgical treatment.