Purpose:We present a large series of eosinophilic cystitis including 8 cases; 3 of them had tumor-like lesions. Materials and Methods: The archives of pathology clinic of Inonu University Medical Faculty were reviewed from 1988 to 2002. The characteristics of patients and their diseases were recorded. Data obtained from 180 cases (172 from the literature and 8 from the present series) was assessed. Results: Seven cases had symptoms such as dysuria, frequency, hematuria, suprapubic pain, and difficulty in voiding. One asymptomatic case with history of bladder carcinoma was diagnosed during routine cystoscopy. The findings were microhematuria in 6 cases, macrohematuria in 2, pyuria in 3, urinary infection in 1, eosinophilia in 1, hyperazotemia in 1, and bladder masses in 3. Cystoscopies detected edematous and erythematous areas in 5 cases and lesions mimicking bladder carcinoma in 3. One case did not take further treatment after cystoscopy and biopsy and completely recovered. Four cases underwent medical therapy with nonsteroidal anti-inflammatory drugs and antihistaminics. They became asymptornatic and control cystoscopies showed no abnormal finding. Two of three patients with mass lesions recovered after steroid therapy following transurethral resection. The lesion in the third recurred and he improved after a second course of steroid therapy. Conclusions: Eosinophilic cystitis is a rare pathology. Sometimes, it may simulate bladder malignancies. Biopsy is mandatory at diagnosis. Usually, it has a benign course and may be treated with fulguration, analgesics, antihistaminics and steroids, although recurrence is possible. Copyright (C) 2003 S. Karger AG, Basel.