A clinical guideline and algorism for interstitial cystitis and hypersensitive bladder syndrome has been developed by a group of East Asian urologists as a revised form of the Japanese guideline for interstitial cystitis. The guideline defines interstitial cystitis (IC) as a disease of the urinary bladder diagnosed by 3 requirements; 1) a characteristic complex of lower urinary tract symptoms, 2) bladder pathology such as Hunner's ulcer and bladder bleeding after overdistension, and 3) exclusions of confusable diseases. The characteristic symptom complex is termed as hypersensitive bladder syndrome (HBS), which is defined as bladder hypersensitivity, usually associated with urinary frequency, with or without bladder pain. For the definite diagnosis of IC, cytoscopy or hydrodistension is crutial; HBS is the diagnosis when IC is suspected but not confirmed by the 3 requirements. Numerous therapeutic options are available; however, most of them lack in high level of evidence, leaving a few as recommended therapies. Etiology of IC are multifactorial; the interaction among nervous, immune and endocrine factors forms a vicious cycle, provocating and maintaining inflammatory reactions in the bladder. The inclusion and efficacy criteria for clinical trials should be standardized to enhance the clinical research for this disabling disease, which has proved to be more prevalent than previously believed.