Over a five-year span 1,134 patients with asymptomatic solitary pulmonary nodules were entered into a cooperative study. Of the 392 lesions found to be primary bronchogenic carcinoma, 67 patients were living and under observation ten years following operation. In the study, 32% of lesions were primary bronchogenic carcinoma, the incidence being 51% in patients above the age of 50 years. "Curative" resection was possible in 309 patients (78.9%) with a five-year observed survival of 38.5% and a ten-year observed survival of 20.1%. Factors that influenced long-term survival were size of lesion, age at operation, and interval between the last normal and the first abnormal x-ray film. Histologic cell type and extent of resection were not found to influence long-term survival.