In Workshop 8 at the International Conference on Interstitial Cystitis (Kyoto March 2003, future research needs for the definition/diagnosis of interstitial cystitis (IC) were discussed by the participants. To structure discussions a study proposal was used. This workshop decided that research should focus on identifying and validating classification criteria for the diagnosis of IC. This might well be done in a (multi-centre) study with a control group of urge-frequency patients without pain (OAB?). However, before doing so standards should be defined as on how to perform and interpret vaginal examination, urodynamic investigation, cystoscopy under anesthesia, potassium sensitivity test, and histopathology in these patients.