Based on clinical assessment alone, patients with stage II non-small cell lung cancer (NSCLC) comprise only 5% of all patients with NSCLC. In addition, patients with stage II NSCLC represent a heterogeneous group, since stage II consists of patients with T1-2N1 or T3N0 tumors. By definition, patients with tumor invading the chest wall apex, mediastinum, diaphragm, or even the mainstem bronchus may all have T3 tumors. The extent of the data available regarding treatment of each of these different groups is therefore limited. The quality of the data is limited as well, because information often comes from small series of patients. Studies of adjuvant therapy after complete resection of stage II NSCLC are an important exception to this generalization, since data from large, randomized studies of adjuvant radiation therapy, chemotherapy, or a combination of the two are available for analysis. Superior sulcus tumors are discussed elsewhere in these guidelines.