Between 1979 and 1989, 876 patients with non-small-cell lung carcinoma were referred to our unit for surgical treatment. One hundred forty-six patients were judged not suitable for surgical treatment on clinical, radiologic, or bronchoscopic findings. Cervical mediastinoscopy or anterior mediastinotomy (or both) showed that 151 patients had mediastinal involvement by invasion or metastases into the ipsilateral (N2 disease) or contralateral (N3 disease) superior mediastinal lymph nodes and were therefore deemed inoperable. Except for one patient who had involvement of a single nodal station at mediastinoscopy, all other patients (n = 578) undergoing thoracotomy were thought, on the basis of computed tomographic scan or mediastinal exploration (or both) not to have N2 disease. Despite our efforts to avoid surgery on patients with N2 disease, at thoracotomy routine mediastinal node dissection disclosed that 149 patients had unsuspected N2 disease. Resection was possible in 130 (87.3%) by pneumonectomy (n = 72), bilobectomy (n = 7), lobectomy (n = 49), or lesser resection (n = 2). In three patients the resection was incomplete (2.3%), but in 127 a complete resection was performed (85%). Histologic examination in these 149 patients showed that 72 tumors were squamous cell carcinoma, 54 adenocarcinoma, 14 large-cell carcinoma, and 9 of mixed type. Eight patients died in the hospital after thoracotomy. Adjuvant therapy was not used after complete resection. Complete follow-up was obtained in 134 patients and the mean follow-up period was 27.25 months (1 to 116 months). The actuarial 5-year survival for those having complete resection was 20.1%. There was a statistically significant difference favoring long-term survival in those patients with squamous cell carcinoma (p < 0.01) and those in whom only one nodal station was involved (p < 0.05). Neither the extent of resection nor the involvement of any specific nodal station influenced long-term survival. Despite rigorous preoperative investigations, routine mediastinal node dissection demonstrated mediastinal node metastasis for the first time at thoracotomy in 26% of our patients. We believe resection is justified in these patients, who have already necessarily incurred the morbidity and mortality of thoracotomy, so long as complete resection is possible.