Claudins are tight junction proteins that are highly expressed in ovarian carcinoma (OC). The objective of this study was to analyze the anatomic site-related expression and clinical role of claudins in OC. Effusions (n = 218), corresponding primary tumors (n = 81), and solid metastases (n = 164) (total = 463 tumors) were immunostained for claudin-1, claudin-3, claudin-4, and claudin-7. Results were analyzed for association with anatomic site, clinicopathologic parameters, and survival. All 4 claudins were expressed in >85% of tumors at all anatomic sites. However, staining extent of all except claudin-4 was significantly higher in effusions compared with both primary carcinomas and solid metastases (P < .001). In univariate survival analysis of the entire cohort, higher claudin-3 (P = .038) and claudin-7 (P = .035) expression in effusions correlated with shorter overall survival (OS), with similar results for claudin-7 in analysis of progression-free survival (P = .026). In separate analysis for patients with prechemotherapy effusions, higher claudin-7 expression correlated with shorter OS (P = .045). For patients with postchemotherapy effusions, higher claudin-1 (P = .018) and claudin-3 (P = .009) expression correlated with shorter OS. In multivariate survival analysis of the entire cohort, claudin-7 expression was an independent predictor of poor progression-free survival (P = .017). Claudin-3 independently predicted poor OS for patients with postchemotherapy effusions (P = .012). With the exception of claudin-4, claudins are upregulated in OC effusions compared with solid tumors, in agreement with our previous data for cadherins and integrins in this cancer type, suggesting a prosurvival role for these surface molecules. Claudin-3 and claudin-7 expression in effusions independently predicts poor survival in OC.