Cadherin-catenin complexes play a key role in embryonic development, and are associated with carcinogenesis and metastasis. We studied the expression of the major members of the family, including E-cadherin and beta-catenin in prostate cancer (PC), and correlated with Gleason grade and pathologic stage. Immunohistochemistry was performed on serial sections of paraffinized radical prostatectomy specimens to evaluate E-cadherin (n = 16) and beta-catenin (n = 17) expression using heat induced epitope retrieval. Benign appearing prostate epithelium was used as an internal control in each specimen. Two pathologists independently reviewed and scored the intensity and extent of immunostaining using a semiquantitative scale. The Mantel-Haenszel method, stratified by reviewer, was used to test for an association among Gleason score, pathologic stage, and the expression of E-cadherin or beta-catenin in PC. Gleason grade > or =7 cancers showed significantly lower expression of E-cadherin and beta-catenin compared to Gleason grade < 7 PC, P = 0.015 and 0.025, respectively. In addition, beta-catenin was down regulated in 4 of 5 (80%) specimens with identifiable high-grade prostatic intraepithelial neoplasia and had demonstrable nuclear staining in higher grade PC (P = 0.0001). However, E-cadherin and beta-catenin membranous or nuclear expressions were not significantly associated with final pathologic stage of the specimens (P values >0.05). Overall, the expression of E-cadherin and beta-catenin is significantly down regulated in PC compared to surrounding benign appearing prostate, which correlates with increasing Gleason grade. Furthermore, nuclear localization of beta-catenin in high grade PC may be a useful biomarker for aggressive PC.