Objective: To study the characteristics of carcinomatous atelectasis under fiberbronchoscopy. Methods:Using fiberbronchoscopy

sputum smear and pathological examination of biospy specimens were studied in 136 atelectasis patients. Results:47 patients with bronchogenic carcinoma proved by fiberbronchoscopy and biopsy. Neopalstic masses of bronchogenic carcinoma were found in 29 patients(61.7%)

invasion of bronchus was found in 15 patients(31.91%) and endobronchial compression in 3 cases(6.38%).In 47 cases

squamous cell carcinoma was confirmed in 25 cases(53.16%)

adenocarcinoma in 4 cases(8.51%) and undifferentiated carcinoma in 17 cases(36.16%). In addition

the pathological findings in 1 patient did not conform to any cell type of the lung cancer. Conclusion:1. Male smoker cases were more than others in carcinomatorus atelectasis for 74.5%. 2. 47 patients(34.55%) with bronchogenic carcinoma proved by fiberbronchoscopy pathology and (or) biopsy were reported in 136 atelectasis patients. 3. Most of obstructive regions showed that cauliflower like masses located in upper lobe of left lung under fiberbronchoscopy

less in middle and lingual lobe.Incidence of bronchial carcinoma was not markedly different between anterolateral segments and posterolateral segments of the various lobes of lung.