Abstract: Objective To investigate the expression and significance of claudin-4 and PTEN in endomentrioid adenocarcinoma. Methods Immunohistochemistry was applied to detect the expression of claudin-4 and PTEN in 75 cases of endomentrioid adenocarcinomas、35 dysplasias and 28 proliferating endometria. Results From proliferative endometrium、endometrial dysplasia to endometrial the positive expression of claudin-4 increased gradually. There was a significant difference between groups (P<0.05). The positive expression of PTEN in three groups showed an increasing trend. The difference was significant (P<0.05).The overexpression of claudin-4 was correlated to myometrialinvasion(P<0.05),but not to histological grade invasion(P＞0.05),histological grade pathologic stage lymph node metastasis nor histological type；the hypoexpression of PTEN was correlated to myometrialinvasion(P<0.05), not to those of the others. Negative correlation was found between claudin-4 and PTEN（r=-0.36, P<0.05） . Conclusion Overexpression of claudin-4 may be involved in carcinogenesis and development of endometrioid adenocarcinoma,and hypoexpression of PTEN may contribute to these process.