Eosinophilic cystitis, a rare disease of unknown origin, simulates bladder neoplasms and interstitial cystitis. Since the first report by Brown in 1959, 35 additional cases have appeared in the literature. Reported here are 3 cases with advanced forms of this disease which failed to respond to antibiotics, antihistamines, steroids, fulguration, and, finally were subjected to cystectomy and urinary diversion after periods of five to fifteen years.