In women symptoms of interstitial cystitis are difficult to distinguish from those of painful bladder syndrome and they appear to overlap with those of urinary tract infection, chronic urethral syndrome, overactive bladder, vulvodynia and endometriosis. This has led to difficulties in formulating a case definition for interstitial cystitis, and complications in the treatment and evaluation of its impact on the lives of women. We performed a systematic literature review to determine how best to distinguish interstitial cystitis from related conditions.