BACKGROUND: Ring Box Protein-1 (RBX-1), a component of SCF E3 ubiquitin ligases, has a crucial role in bladder urothelial cell carcinoma (UCC) carcinogenesis and progression. OBJECTIVES: In the present study, it is aimed to determine the expression of RBX-1 protein in bladder UCC and the association between tumor grade, stage and RBX-1 expression. METHODS: Ninety UCC samples and 20 samples containing foci of normal bladder urothelium were recruited and analyzed immunohistochemically in terms of RBX-1 expression. Immuno-reactivity scoring system (IRS) was used to determine RBX-1 expression levels. RESULTS: RBX-1 overexpression was associated with high tumor grade (p= 0.001) and advanced stage (p= 0.001). pT1 tumors showed higher RBX-1 expression than pTa tumors. pT2 tumors showed not only higher expression than pTa tumors but also higher expression than the total of pTa and pT1 groups combined. There was no statistically significant relation between RBX-1 expression and patient gender (p= 0.116) or age (p= 0.191). CONCLUSIONS: In bladder UCC, RBX-1 overexpression is associated with high tumor grade and advanced stage and represents biological potential of invasiveness and aggressive disease. Results of the present study have to be supported with further studies to reveal clinical and therapeutic implications of RBX-1 overexpression in bladder UCC.