Cholesteatoma is a chronic inflammation of the middle ear, which leads to a progressive bony destruction of the petrous bone. Main symptoms are fetid otorrhea, hearing loss and dizziness. Left untreated, cholesteatoma may be fatal due to intracranial complications. The following overview is intended to illustrate the current and generally recognized knowledge of genesesi, clinical symptoms und preoperative diagnostical procedure. Surgical therapie will be focussed in a second part.