Isolated vasculitis involving the bladder is rare. We describe a case of irritative voiding and hematuria with slightly elevated inflammatory parameters. In order to exclude a neoplastic process we performed cystoscopy and computed tomography. Secondary systemic causes such as lupus erythematosus or rheumatoid arthritis were excluded. Cytopathological examination of the biopsies showed necrotizing vasculitis of the small bladder vessels, which responded to treatment with steroids and cyclophosphamide.