A 53-year-old previously healthy woman suddenly developed adult respiratory distress syndrome (ARDS) of unknown etiology. High-dose corticosteroid pulse therapy and artificial ventilation were started immediately and she dramatically responded to the treatment. However, soon after recovery from ARDS, she developed typical rheumatoid arthritis (RA). Although no apparent relationship between RA and ARDS was clear, this case is quite suggestive in the consideration of the etiology of ARDS.