Abstract: Utlizing an immunohistochemical method to detect keratin(KER) and careinoembryonic antigen (CEA) in 51 carcinoma tissues biopsied by fiber brochoscope. 5 cases normal bronchial mucous and lung tissue-control group. The results: CEA was negative in all cases of control group. The positive rate of CEA was 62% in all of the 50 lung cancer cases. In each pathologic type lung cancer, there was no significant difference between confirmed group and dudious group both in positiverate and staining intensith of CEA and KER. There was significant difference between squdrious carcinoma and adenocareinoma in postive rate and stainging intensity of KER staining. The positive rate of KER in small cell carcinoma of lung was 90%.We suggested that CEA staining be used in qUaliwhve diagnosis of lung carcinoma for tissues biopsied by fiber brochosccpe, KER staining give some help on diffeedal diagnosis between squamious careinoma and adenocareinoma of lung. The high positive rate of KER staining in small cell carcinoma supports the view that both small cell and no-small cell caxcinornas originate from stem cell.