The chromosome segregation 1-like (CSE1L) protein is highly expressed in most cancers and has been shown to be secreted by tumor cells. We studied the presence of CSE1L in the urine of patients with bladder urothelial carcinomas. The results of our immunohistochemical analysis showed a high expression of CSE1L in bladder cancer specimens, while the normal bladder specimens only showed a very faint staining in some cells. Immunoblotting showed that CSE1L was present in urine of patients with bladder cancer. Urinary CSE1L-positive cases were detected in 95% (57/60) of patients with bladder urothelial carcinomas or the atypical/suspicious cases with urothelial atypia. No CSE1L was detected in urine of healthy controls (p<0.01). Our results suggest that urinary CSE1L deserves further evaluation for the screening of bladder cancer.