Objective To evaluate the clinical value of fluorescence in situ hybridization (FISH) method for diagnosis of bladder urothelial carcinoma.Methods Urine samples from 81 patients suspected of having bladder urothelial carcinoma were collected for immediate urine cytology and FISH analysis.All patients underwent cystoscopy for identification of bladder lesions.Urine samples from 8 patients with benign disease of urinary system werealso analyzed by means of FISH and cytology.The sensitivity and specificity of FISH were compared with cytology.Results 81 subjects of bladder urothelial carcinoma were verified with pathology,which included 34 non-muscle invasive carcinoma,14 cases with muscle invasive carcinoma,42 cases with high-grade carcinoma,and 24 cases with low-grade carcinoma.Residual cases included 12 verified benign disease of urinary system,and to serve as controls with 8 patients with benign disease of urinary system.The sensitivities of FISH,cytology and cystoscopy were 72.8％,27.2％ and 97.5％.The sensitivity of FISH was superior to cytology,but inferior to cystoscopy.The specificity and diagnostic concordance rate of FISH and cytology were 85.0％,100.0％ and 75.2％,41.6％,respectively.Conclusion FISH analysis as a non-invasive method has good sensitivity and specificity for diagnosing bladder urothelial carcinoma.