Abstract/Text: We have attempted to design classification criteria for adult Still's disease by analyzing the data obtained through a multicenter survey of 90 Japanese patients with this disease and of 267 control patients. The proposed criteria consisted of fever, arthralgia, typical rash, and leukocytosis as major, and sore throat, lymphadenopathy and/or splenomegaly, liver dysfunction, and the absence of rheumatoid factor and antinuclear antibody as minor criteria. Requiring 5 or more criteria including 2 or more major criteria yielded 96.2% sensitivity and 92.1% specificity. However, an exclusion process will be needed for an accurate classification, since this disease is relatively rare.