We report two Japanese women with severe hepatic dysfunction and adult onset Still's disease. A 51-year-old woman had been diagnosed with adult onset Still's disease 3 years earlier. She relapsed while on maintenance therapy with prednisolone and methotrexate. After induction of remission with methylprednisolone pulse therapy, indomethacin, and methotrexate, severe hepatic failure occurred. This patient lacked the typical symptoms of adult onset Still's disease. The second patient was a 32-year-old woman with typical adult onset Still's disease. Remission was induced by high-dose prednisolone and methylprednisolone pulse therapy plus cyclosporine. After she stopped cyclosporine, severe liver dysfunction occurred. In both patients, liver dysfunction occurred during high-dose steroid therapy, and oral cyclosporine (3 mg/kg per day) dramatically improved their liver function. When steroid-resistant severe hepatic failure occurs in patients with adult onset Still's disease, cyclosporine may be the immunosuppressant of choice.