The results of surgical treatment were analyzed for 102 patients with non-small cell lung cancer invading the mediastinum by direct extension (T3 and T4), but those who had N2 disease were excluded to eliminate the adverse prognostic effect of this nodal subset. The histologic type was squamous cell carcinoma in 55 patients, adenocarcinoma in 40, and large cell carcinoma in 7. There were 58 T3 tumors invading the mediastinal pleura or fat, phrenic nerve, vagus nerve, pericardium, or pulmonary vessels and 44 T4 lesions invading the aorta, vena cava, esophagus, trachea, spine, or atrium. Resection included lobectomy (33 patients), pneumonectomy (32 patients), and limited resection (6 patients). Complete resection was possible in 46 patients and incomplete or no resection was possible in 56. The interstitial implantation of radioactive sources to control residual tumor also was undertaken in 43 patients. The operative mortality was 6%. The overall survival (Kaplan-Meier) was 19% at 5 years (median survival time, 18 months). Factors found to be significantly affect survival were complete resectability and the histologic type. With complete resection, the 5-year survival was 30% (p = 0.005). The 5-year survival in patients with adenocarcinoma or large-cell carcinoma was 30%, compared with 14% in patients with squamous cell carcinoma (p = 0.002). The extent of mediastinal involvement (T3 versus T4) influenced resectability and survival, and this approached statistical significance (p = 0.055). We conclude that most patients with non-small cell carcinoma and mediastinal invasion do poorly with primary surgical treatment.