The contacts between epithelial cells are maintained mainly by adherens junctions and tight junctions (TJs). However, the role of TJ proteins in cancer is not well understood. We studied the expression of occludin and 4 claudins to assess their importance in the progression of urothelial carcinoma of the upper urinary tract (UC-UUT). In 129 cases, we examined their expression using immunohistochemical analysis and also their relationships to clinicopathologic parameters and clinical outcome. Positive expression of occludin and claudins 1, 3, 4, and 7 were recognized in 117 (90.7%), 113 (87.6%), 95 (73.6%), 127 (98.4%), and 123 (95.3%) of tumor samples, respectively. Claudin-3 expression was significantly associated with stage, grade, and pattern of growth. Claudins 1 and 4 expression was significantly associated with stage. However, neither occludin nor claudin-7 expression was associated with clinicopathologic findings. When tumors with scores below the median for a given protein were classified as the "low expression group," univariate analysis of overall survival revealed that claudins 1 and 3 had a significant effect on overall survival. Detection of claudins 1, 3, and 4 would seem to provide valuable information about the progression of UC-UUT.