Objective To evaluate the clinical outcomes of intravesical instillation of resiniferatoxin (RTX) for the treatment of overactive bladder(OAB). Methods 30 patients (28 females and 2 males) included in the study.The mean age was 39 years (range,21 to 60 years).The mean course of the illness was 6.9 years (range,2 to 30 years).The voiding diaries of pretreatment showed that frequency at day time varied from 9 to 26 times with a mean of 15.0 times;frequency at night ranged from 3 to 13 times with a mean of 6.4 times.Of the 12 patients undergoing cystoscopy 10 had chronic inflammation in both mucous and submucous.Based on biopsy 1 case was pathologically diagnosed as glandulous cystitis,2 as interstitial cystitis,and others as chronic inflammation.100 ml of RTX at a concentration of 100 nmol/L was intravesically instillated in all the patients and was retained within the bladder for 30 minutes. Results RTX instillation had no vesical irritation and other adverse effects,and no local anesthesia was required.The symptoms were improved immediately in all the patients after 1 day of RTX intervention.The decreases in both diurnal (5 to 15 times,mean 8.9 times) and nocturnal (0 to 5 times,mean 3.0 times) frequencies were significant(P