Two anatomic subsets of patients with stage IIIa non-small cell cancer of the lung are candidates for definitive surgical treatment. The first group includes patients with T1, T2, or T3 primary tumors and regional lymph node metastases confined to the ipsilateral mediastinal and subcarinal lymph nodes (N2 disease). There is controversy over the selection of this group of patients for surgery; some physicians do not believe that resection is an option if there is any evidence of mediastinal lymph node involvement. The second group is composed of patients with limited, circumscribed extrapulmonary extension of the primary tumor and lymph node metastasis, if present, limited to the hilar and peribronchial nodes (T3 N0-1 M0 disease). Peripheral tumors invading the chest wall, tumors originating in the superior sulcus of the lung, and those with limited involvement of the pericardium or the main bronchus are included. A five-year cumulative survival rate of 28 percent was documented for 198 consecutive patients undergoing complete resection for stage IIIa non-small cell lung cancer, 21 percent for the T1-3 N2 group, and 39 percent for the T3 N0-N1 patients. Cell type was not a statistically significant variable for survival; however, a superior outcome was observed for patients with squamous cell carcinoma in every TNM category. The results support surgical treatment as a valid option for selected patients with extrapulmonary extension of the disease.