Background: Fiberoptic bronchoscopy (FOB) is frequently used to diagnose and stage bronchogenic carcinoma (BC). However, the value of FOB in diagnosis/staging BC presenting as a pulmonary nodule or mass (PNM) is controversial. Since chest CT is usually obtained in these patients, it may be used in patient selection for preoperative FOB. Objective: Evaluation of the role of chest CT in determining the predictive value of FOB in diagnosing/staging a PNM, by comparing the results of CT and bronchoscopy. Design: Retrospective review of chest CTs and medical records. Patients: Consecutive patients with BC between 1992 and 1994 who had diagnostic FOB and CT in our institution, but without radiographic evidence of (1) pulmonary atelectasis, (2) endobronchial tumor or narrowing of the central airways, and (3) the PNM abutting the central airways. Results: Sixty-four patients met the selection criteria. The size of the PNM ranged from 1.5 to 10 cm; the size was ≤4 cm in 62 patients. FOB provided a diagnosis in 22 patients. Bronchoscopy detected endobronchial lesions in 11 patients (17%); 3 had lesions in more than one lobe. In three patients, the PNM was <3 cm. The radiographically undetected endobronchial tumor increased the tumor stage in only two patients. The 'CT bronchus' sign had a positive and negative predictive value of 75% and 68%, respectively. Conclusions: (1) In this study, CT failed to detect endobronchial tumor in 11 of 64 patients (17%). Because of the implications of a new staging system, more studies are necessary before abandoning staging FOB. (2) The CT bronchus sign has a very high positive and negative predictive value in the use of diagnostic FOB and should be used to guide the method of biopsy of a PNM.