A 24-year-old woman was admitted to our hospital because of a high fever that had persisted for two weeks. She complained of a sore throat and arthralgia, and had evanescent rash, lymphadenopathy, liver dysfunction, and hyperferritinemia. Tests for RF and ANA were negative. Adult-onset Still's disease was diagnosed. On the fifth day of hospitalization, acute respiratory distress syndrome (ARDS) and disseminated intravascular coagulation (DIC) developed. Treatment consisted of mechanical ventilation and administration of steroid pulse-therapy and gabexate mesilate. Analysis of fluid obtained by bronchoalveolar lavage showed increases in the total cell count, predominantly of neutrophils and lymphocytes. Bilateral pulmonary infiltration seen on chest radiographs was alleviated, and the arterial blood gas data gradually improved. After cyclosporine was given, all the above symptoms associated with adult-onset Still's disease disappeared. Plasma levels of inflammatory cytokines decreased with the improvement of the patient's clinical condition.