We retrospectively analyzed the clinical relevance of hydrodistention under anesthesia for patients having urgency and/or lower abdominal pain who were clinically diagnosed as having interstitial cystitis (IC) from May 1996 to May 2005. Their symptoms were refractory to anticholinergic or antiinflammatory agents. Hydrodistention was performed under general or spinal anesthesia with direct vision by cystoscopy and irrigation fluid was instilled into the bladder at a pressure of 80 cmH2O. Cystoscopic findings revealed glomerulation in 26 patients (96%), cracking in 10 (37%) and Hunner's ulcer in 3. Twenty-four patients (89%) obtained improvement of the objective symptoms after treatment. However, symptoms soon deteriorated in 16 patients, and the average duration of efficacy was only 4.7 months (SD; +/-3.7). There were two episodes of complication in this treatment. Bladder rupture occurred during hydrodistention, but was successfully managed with simple percutaneous perivesical drainage. One patient with acute pyelonephritis was treated with an antimicrobial agent without any additional treatment. Although bladder specimens were examined by immunohistochemistry, tryptase and c-kit were not linked with the mast cell count, severity of symptoms or treatment efficacy. Hydrodistention of the bladder may be recommended as the first treatment choice for patients with IC because it provides relatively high efficacy. However, the short duration of the efficacy requires a second-line treatment option for better management of patients with IC.