Lung cancer often requires an invasive surgical procedure to document inoperability. Using a fiberoptic bronchoscope with a flexible needle that can penetrate the walls of the trachea and major bronchi, we sampled mediastinal and hilar lymph nodes in 32 patients. Of 18 patients presenting with a diagnostic problem, 11 had aspirates that were positive for cancer. Surgery in 6 of the remaining 7 showed cancer in 4 (false negative). Ten other patients presented with a staging problem. Four had positive mediastinal aspirates; 3 of these 4 had a normal or equivocally normal mediastinum on chest roentgenogram. Surgery in 4 of the remaining 6 showed no cancer in 4 (true negatives). The procedure was also diagnostic in 2 of 4 patients with recurrent mediastinal small cell carcinoma and in 3 patients with intrabronchial necrotic tumors. There were no complications. We conclude that this is a safe, easily performed procedure that can replace more invasive procedures in the diagnosis and staging of lung cancer.