Congenital cholesteatoma, a rare disease, originates from the ectoderm that forms the primitive notochord. Embryonic cell rests from this ectodermal structure may occur in any of the cranial bones. Congenital cholesteatoma of the temporal bone may occur in the petrous apex ; the mastoid ; the middle ear ; both middle ear and mastoid ; and the external auditory canal. The following points are emphasized in defining congenital cholesteatoma of the tympanum and mastoid ; 1) development behind an intact tympanic membrane, 2) without previous history of aural infections, 3) arising from embryonal cell inclusion of squamous epithelium. An 10 years old male patient had been suffering from the right postauricular fistula for 3 months. He had no history of previous ear disease. Normal tympanic membrane was noticed on the otoscopic examination, and normal findings were encountered on the pure tone and impedance audiometry. X-ray examination revealed a large radiolucent defect on the right mastoid, Intact wall mastoidectomy was done under general anesthesia. The cholesteatoma materials were filled in the right mastoid and aditus antrum, but middle ear and ossicular chain were not involved. Cholesteatoma was confirmed by biopsy. We report this case with review of literatures.