Inverted papillomas are primarily lesions of the lateral nasal wall, but similar papillomas have been observed on the nasal septum. There is controversy as to whether papillomas on the septum should be considered differently from those of the lateral nasal wall and paranasal sinuses. A review of the records of the Massachusetts Eye and Ear Infirmary, Boston, disclosed 18 cases of inverted papilloma of the nasal septum that were treated before January 1968 and January 1980. The histologic diagnosis of inverted papilloma was confirmed by pathologists who examined histologic slides from these cases; these slides had been randomly mixed with slides of nasal vestibule squamous papillomas and slides of inverted papillomas of the lateral nasal wall. Squamous papillomas of the vestibule were readily distinguished microscopically from inverted papillomas of the septum and lateral wall that were histologically similar. The clinical course of these patients suggests that inverted papillomas of the nasal septum behave like inverted papillomas elsewhere and require wide surgical excision and careful follow-up.