A 58-year-old Japanese woman developed spiking fever, polyarthralgia and hepatosplenomegaly, with highly elevated levels of c-creactive protein (CRP) and ferrtin, and elevated erythrocyte sedimentation rate (ESR). The AOSD was diagnosed according to the Yamaguchi-criteria of 1992. She was first treated with a combination of prednisolone (20 mg/day) and oral methotrexate (MTX) (7.5 mg/week). This combination, however, was not effective with tapering the dose of prednisolone. When a high dose of cyclosporin A (CyA) (5.5 mg/kg/day) was then added to MTX (5 mg/week), the patient's fever and polyarthralgia decreased, and her elevated serological parameters such as CRP and ESR also gradually declined. Finally, the dose of prednisolone was tapered to 10 mg/day. Only a few cases of AOSD treated with CyA plus MTX have been reported. Thus, further careful observation will be needed to establish the usefulness of this drug combination as a therapy for AOSD.