Residual tumor (R1) was proven at the proximal bronchial resection margin in 88 (3.6%) of 2464 cases of lung cancer following lung resection and standard lymph node dissection. Postoperative complications (8%) were: fistula of the bronchial suture line (n = 7), bleeding (n = 2) and heart luxation (n = 1). The in-hospital mortality was 16.6%. Causes of death were: bronchial fistula (n = 7), erosion of the pulmonary artery (n = 4), respiratory failure (n = 1), and empyema (n = 1). Forty-three patients received postoperative radiation therapy. Median survival of all patients following incomplete resection was 16 months, compared to 37 months following complete resection (P < 0.001). Length of survival was independent of tumor stage, histology, site of infiltration and postoperative radiation. In conclusion, in resection for lung cancer clear margins should be verified by intraoperative frozen section. In the case of residual tumor at the bronchial resection margin, wider resection is mandatory in stage I and II if the patient meets the functional criteria. Even in stage III a and III b prognosis is significantly better after complete resection than R1-resection; the difference, however, is smaller than in lower stages.