Objective: To evaluate the safety and efficacy of intravesical instillation of hyaluronic acid/chondroitin sulfate in the treatment of refractory painful bladder syndrome. Material and methods: Forty patients were subjected to intravesical instillations of hyaluronic acid/chondroitin sulfate weekly for 4 weeks and at 6., 8., 12. and 16. weeks, afterwards. Then we evaluated the efficacy of this treatment modality by determining the mean changes in visual analogue scale (VAS) pain score, the pelvic pain and urgency/frequency questionnaire, the O’Leary-Sant interstitial cystitis symptoms index/ problems index and 3 day-voiding diary results including daily number of voids and mean voided volume at 2 weeks, 3, and 9 months after the last dose (4th month) and urodynamic studies including cystometric capacity, 1st sensation of urination, and Q-max at 9 months after the last dose. ORCID IDs of the authors: H.S. 0000-0002-9621-4630; A.S. 0000-0002-3215-4843; W.K. 0000-0002-4102-5525; T.O. 0000-0002-8711-7417; A.F. 0000-0001-6267-2572; A.M. 0000-0003-4429-7451; A.E. 0000-0003-2251-2392. Department of Urology, Benha University, Benha, Egypt Submitted: 25.04.2018 Accepted: 22.08.2018 Available Online Date: 21.11.2018 Corresponding Author: Hammouda Sherif E-mail: hammoda_elsherif@yahoo.com ©Copyright 2019 by Turkish Association of Urology Available online at www.turkishjournalofurology.com Results: Thirty-seven patients (6 males 16.2%, 31 females 83.8%) completed the entire follow-up protocol of this study. Age of the patients ranged from 22 to 37 years (mean, 30.7±4.18 years) and their body mass indexes (BMIs) ranged between 29 and 37 kg/m2 (mean, 33.5±2.58 kg/m2). An initial response to treatment in all parameters at variable degrees was noticed at 2 weeks after the last instillation when compared to the baseline, and these changes were statistically significant (p |