Purpose: Our study aims to evaluate the efficacy of hyaluronic acid (HA) on interstitial cystitis patients admitted to our clinic with the diagnosis of bladder pain syndrome/interstitial cystitis (BPS/IC). Material and methods: The pre- and post-treatment symptom scores the severity of symptoms, and cystoscopic and pathologic findings of 23 patients diagnosed with BPS/IC were prospectively evaluated between 2009-2013. The O'Leary-Sant Interstitial Cystitis Symptom Index (ICSI), Interstitial Cystitis Problem Index (ICPI) Scale, and Pelvic Pain and Urgency/Frequency Patient Symptom Scale (PUFSS) were used as questionnaire forms. 40 mg HA was administered intravesically for 6 weeks. Results were reviewed in patients who completed the treatment. Results: Two patients discontinued the treatment, 21 patients were enrolled in the study. The mean age was 48 (33-78). 20 patients underwent cystoscopy surgery. While 8 of them showed nonspecific changes in the trigonum area, 12 had no pathologies. While the mean ICSI score of the 21 patients who filled out the ICSI/ICPI and PUFSS questionnaire forms was 15.6 (12-20) pretreatment and 9.2 (1-18) post-treatment (p<0.01), the mean ICPI score was 13.1 (7-16) pre-treatment, and 7.8 (0-16) post-treatment (p<0.01). The mean PUFSS score was 23.9 (14-35) pre-treatment, and 16.4 (5-31) post-treatment (p<0.01). While the mean PUF symptom score was 16.1 (10-23) pre-treatment, and 10.9 (3-19) post-treatment (p<0.01), the mean PUF quality of life score was 7,8 (4-12) pre-treatment, and 5.5 (1-12) post-treatment (p<0.01). No side effects were found in the patients. Conclusion: Intravesical HA therapy is a safe treatment option in the treatment of BPS/IC. While it has a certain degree of efficacy, further prospective, randomized, placebo-controlled studies with a larger study population are required.