To assess the intravesical application of immunotoxin as adjuvant therapy to prevent recurrence after tumor resection in bladder cancer patients Methods An anti human immunotoxin against bladder carcinoma, BDI 1 RT, was prepared and its in vitro targeting cytotoxicity estimated The immunoreactivity of BDI 1 RT with human bladder cancer tissue of different grades and stages was detected by immunohistochemical analysis After safety test, intravesical administration of BDI 1 RT was performed in 31 patients while mitomycin C (MMC) was used in 36 patients serving as a control group The recurrence rates and side effects in both groups were recorded In addition, the development of human anti mouse antibodies (HAMA) was determined by ELISA, to assess the potential safety of this immuotoxin Results In our study, BDI 1 RT had immunoreactivity with 81 6% of bladder transitional cell carcinomas The immunoreactivity of BDI 1 RT correlated with tumor grade High grade carcinoma had stronger staining than low grade ( P <0 05) There was no significant difference between the BDI 1 RT group (10%) and MMC group (19 3%) in recurrence rate ( P >0 05) Side effects, including systemic and local, were more frequent in the MMC group (11 of 36 patients versus 2 of 31, P <0 05) HAMA was not detected in any of 7 patients Conclusion Immunotoxin may have considerable potential in the prophylaxis of bladder transition cell carcinoma To assess the intravesical application of immunotoxin as adjuvant therapy to prevent recurrence after tumor resection in bladder cancer patients Methods An anti-human immunotoxin against bladder carcinoma, BDI 1 RT, was prepared and its in vitro targeting cytotoxicity estimated The immunoreactivity of BDI 1 RT with human bladder cancer tissue of different grades and stages was detected by immunohistochemical analysis After safety test, intravesical administration of BDI 1 RT was performed in 31 patients while mitomycin C (MMC) was used in 36 patients serving as a control group The recurrence rates and side effects in both groups were recorded In addition, the development of human anti mouse antibodies (HAMA) was determined by ELISA, to assess the potential safety of this immuotoxin Results In our study, BDI 1 RT had immunoreactivity with 81 6% of bladder transitional cell carcinomas The immunoreactivity of BDI 1 RT correlated with tumor grade High grad There were no significant differences between the BDI 1 RT group (10%) and MMC group (19 3%) in recurrence rate (P> 0.05) Side effects, including systemic and local, were more frequent in the MMC group (11 of 36 patients versus 2 of 31, P <0 05) HAMA was not detected in any of 7 patients Conclusion Immunotoxin may have considerable potential in the prophylaxis of bladder transition cell carcinoma