Still's disease was reported to be a type of Juvenile Rheumatoid Arthritis (JRA) by Still in 1897. Adult-onset Still's disease is an important clinical entity inducing fever, skin rash and polyarthritis. Spiking fever and rash are characteristic features for early diagnosis. Although chronic polyarthritis is similar to RA, ankylosis of hand joint is characteristic for Still's disease rather than destructive change. Increased ESR, negative autoantibodies, leukocytosis, liver dysfunction and hyperferritinemja are major laboratory findings. A markedly increased level of serum ferritin can be used, not only as an indicator of disease activity, but also as a diagnostic marker of the disease. For therapy, a moderate dose of steroid is the most effective.