The interum results of a multicenter study on extended segmentectomy for small lung tumors and the results reported by Lung Cancer Study Group are discussed. The multi-center study was started in 1992. The inclusion criterium was the presence of a peripheral tumor of less than 2 cm in diameter on chest X-ray films. Seventy three patients were initially enlisted for the study, but 18 patients underwent lobectomy instead because of various reasons such as true or false-positive N1 or N2 disease. The remaining 55 patients were enrolled in this study. The lymph nodes around the segmental and lobar bronchi were examined during operation using fronzen section. Dissection or sampling of the mediastinal lymph nodes was documented. The amount of lung tissues resected was actually more than one segment, because the resection line far entered the adjacent one. Five patients died; one due to local recurrence, known to have the close resection line to the tumor and one of acute myocardial infarction, one of cerebral stroke, one for esophageal cancer and one due to pulmonary metastases on the non-affected side, with no evidence of local recurrence except the first patients. The interim results suggest that the extended segmentectomy is suitable for patients with N0 small tumors.