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/chon-droitin 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.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<0.001). Progressive improvement in all test parameters was noticed at 3 months after treatment, and this improvement was statistically significant com-pared with baseline and 2 weeks after treatment, respectively (p<0.001).Conclusion: Intravesical instillation with both hyaluronic acid/chondroitin sulfate in the treatment of re-fractory painful bladder syndrome is safe, effective and well tolerated by all patients with no recorded side effects.