Objective:Our aim was to evaluate the relationship of E-cadherin（EC） expression with the biological behavior of lung cancer.Methods:The EC expression and the cellular DNA ploidy were measured using flow cytometry and immunofluorescence methods in 39 cases of primary non-small cell lung cancer. Systemic pathological examination were performed for all cases.Results:The EC expression significantly reduced in all cases of lung cancer.Fluorescene index(FI) of EC expression was (0.90±0.10) in normal lung tissue， (0.49±0.09) in squamous cell lung cancer,(0.63±0.08) in adenocarcinoma.The expression of EC in squamous lung cancer greatly decreased in poor differentiation and with lymph node metastasis (P<0.01).In squamous cell lung cancer,the expression of EC was lower in uneuploid cancer than that in diploid cancer (P<0.05).The expression of E-Cadherin in squamous cell lung cancer reduced more in TNM Ⅲ than in TNM Ⅰ,Ⅱ.Conclusion:The expression of EC decreased in poor differentiation squamous cell lung cancer with lymph node metastasis. In lung adenoma, the decrease in the expression of EC has no relatoin with the TNM stage, lymph node metastasis, and DNA ploidy.