An 18-year-old woman was admitted to the medical center near her home with complaints of high fever and severe headache in June 1995. A diagnosis of adult-onset Still's disease was suspected and 50 mg/day of prednisolone was orally administered. In early April 1997, the patient suffered from sudden bilateral hearing loss and high fever. Pure tone audiogram taken at the same time showed an asymmetric bilateral neurosensorial hearing loss. A diagnosis of Cogan's syndrome was made. Administration of 60 mg prednisolone daily improved fever. Audiogram taken one month after administration of prednisolone showed improvement in the right ear. Monthly cyclophosphamide pulse therapy 700 mg combined with oral prednisolone was instituted. This combination therapy enabled the successful tapering of prednisolone without recurrence of hearing loss. Combined corticosteroid and pulse cyclophosphamide therapy would appear to be one effective regimen for Cogan's syndrome.