During inspection with a flexible bronchoscope, the operator may discover apparent narrowing of a segmental bronchus. Use of the technique of saline solution distension in this circumstance can help the bronchoscopist in the assessment of the underlying nature of the narrowing, although sensitivity will be low. If the bronchus distends easily when saline solution is instilled, this indicates that fixed narrowing due to peribronchial tumor is less likely. There were 21 cases in our study in which a narrowed bronchus had easily distended with saline solution, revealing a macroscopically normal distal airway. All subjects had negative cytology findings, although 3 of 13 subjects did have CT-scan findings suggestive of peribronchial tumor. If the narrowed bronchus is nondistendable, the chances of an underlying tumor in the airway are much greater. In our study, 15 of 17 patients (88.2%) with a fixed narrow bronchus had evidence of a peribronchial tumor by cytology and/or histology results, or CT-scan findings. Only one patient had an apparently fixed narrow bronchus at flexible bronchoscopy but no evidence of tumor on a CT scan or from cytology/histology.