For the period from June 1988 to July 1991 we studied 29 patients who were judged to have operable disease before mediastinoscopy on clinical criteria[absence of distant metastases, phrenic or laryngeal nerve paralysis, positive scalene node biopsy, and malignant pleural effusion]. All patients had computed tomography and mediastinoscopy prior to operation. In the present study, the sensitivity, specificity, and accuracy of CT were 92%, 56%, and 72%, respectively. And the sensitivity, specificity, and accuracy of mediastinoscopy were 92%, 100%, and 97%, respectively. We concluded that because of the low accuracy of CT, CT cannot replace mediastinoscopy, and routine mediastinoscopy should be performed in preoperative staging of bronchogenic carcinoma.