Objective To study the safety and efficacy of transurethral resection of bladder tumor(TURBt)under block anesthesia of bilateral obturator nerves.Methods Seventy-seven patients were chronologically divided into two groups.Forty-six of patients with lateral,bilateral or multiple tumors in the bladder,which underwent transurethral resection of bladder tumor under epidural anesthesia from April 2003 to October 2004,were chosen as the Control Group.Thirty-one patients whom were administrated with epidural anesthesia plus bilateral block of the obturator nerve from October 2004 to July 2005 served as the Study Group.Incidences of bladder perforation and obturator nerve reflex were compared between the two groups.Results In the Control Group,obturator nerve reflex occurred in 25 patients(including intense reflex in 11 patients),giving an incidence of 54.3%(25/46),and bladder perforation resulted from the reflex was observed in 8 patients,with an incidence of 17.3%(8/46).In the Study Group,slight obturator nerve reflex happened in 3 patients(9.9%,3/31)and bladder perforation was found in 1 patient(3.2%,1/31).A significant higher rate of obturator nerve reflex was noted in the Control Group than in the Study Group(?2=15.970,P=0.000),but no statistical difference was seen in bladder perforation rate between the two groups(?2=2.359,P=0.125).Conclusions Bilateral block of the obturator nerve can improve the safety remarkably during transurethral resection of bladder tumor,especially when the tumor was located in the lateral bladder wall.