Carcinoma of the frontal sinus is rare. Treatment is controversial, and prognosis is poor, The etiology is unknown, although some risk factors for other paranasal sinus carcinomas have been identified. A 70-year-old male presented with proptosis and x-ray findings consistent with a mucocele of the frontal sinus. At operation the patient was felt to have a cholesteatoma. Pathologic diagnosis was verrucous carcinoma of the frontal sinus. The case is discussed and the literature is reviewed.