Objective To investigate the expression and clinical significance of Claudin-4 in human se-rous ovarian cancer.Methods 43 cases of serous ovarian cancer from Oct.2008 to May 2014 were studied.Re-al-time quantitative PCR( qRT-PCR) was applied to detect mRNA expression of Claudin-4 in serous ovarian cancer ( n=43 ) in comparison to the corresponding tumor-adjacent tissues.The protein expression of Claudin-4 was measured by immunohistochemistry( IHC) .Results mRNA and protein expression level of Claudin-4 was signif-icantly higher in serous ovarian cancer tissues than in adjacent normal tissues(P<0.05).The high expression of Claudin-4 protein was also associated with large tumor size, lymphatic metastasis, and advanced TNM stage( P<0.05 ) .Conclusions The expression of Claudin-4 is significantly higher in serous ovarian cancer tissues than in the adjacent normal tissues, and it is associated with clinicopathological features.Claudin-4 may become a new marker in early diagnosis and biological target therapy.