Hypothesis / aims of study Overactive bladder syndrome (OAB) is a common condition with a negative impact on quality of life. Botulinum toxin is commonly used. Despite the favorable outcomes seen using Botulinum toxin A ,the method of injection and side effects still need to be solved . Our aim is to use Botulinium toxine with simple method and check its safety and efficacy. Study design, materials and methods 82 patients with refractory OAB were included in this study. Inclusion criteria was refractory non neurogenic OAB not responding to conservative management for at least 3 months. After written consent, Patients were randomly divided into two groups.Group A 45 patients received Botulinium Toxin A 100 unit intravesical instillation diluted in 50 cc normal saline , Group B 37 patients received placebo in the form of 50 cc normal saline by the same method. Patients were evaluated initially by history,physicalexamination,overactive bladder symptom score (OABSS),quality of life symptom score (QOLSS),urine analysis ,routine Laboratory investigations,KUB,Pelviabdominal ultrasound and urodynamics. Patients were followed up at one, and two month post instillation for efficacy and safety by OABSs ,QOL score ,side effects and postvoid residual urine. Results No significant age difference was found in both groups (mean age of Group A was 30.2+8.37 and Group B 31.4+7.11).Significant improvement in OABSS,(from 9.46 + 1.8 to3.1 + 2.1, and 2.8 + 2.5 )and QOLSS ( from42.2 + 1.2 to 83.8 + 6.6,and 83.2 + 8.1) was found in Group A while not in Group B at one and two months follow up(p