A case of familial clustering of interstitial cystitis (IC) and chronic pelvic pain syndrome (CPPS), a symptom complex similar to IC that occurs in men, is reported. The proband was a 28-year-old woman with a 6-month history of severe frequency, urgency, and genital pain. After cystoscopy with hydrodistention and biopsy, a diagnosis of IC was made. IC was also diagnosed in the patient's mother and in two of her brothers, previously considered to have CPPS (category IIIB CPPS). A third brother was asymptomatic. This case highlights the importance of genetic factors in the onset of symptoms and natural history of IC and CPPS.