Acute febrile juvenile rheumatoid arthritis (JRA) of adult onset is often diagnosed by ruling out other problems. The classification of JRA is primarily based on the distinct type of onset, of which there are usually three: (1) acute febrile or Still's type, (2) polyarticular, and (3) monoarticular pauciarticular arthritis. Fever of unknown cause is frequently the initial symptom. This type of arthritis may be characterized by any or all of the following: unexplained high fever, rash, weight loss, lymphadenopathy, splenomegaly, pericarditis, pleurisy, pneumonitis, abdominal pain, myalgias, arthralgias, arthritis, sore throat, leukocytosis, anemia, circulating immune complexes, liver test abnormalities, and carpal-metacarpal and tarsal-metatarsal fusion. Patients often respond dramatically to anti-inflammatory agents. Corticosteroids, gold salts, penicillamine, and cytotoxic drugs have been effective for certain patients. The prognosis of the disease has been generally favorable. Although symptoms may recur, remission can be prolonged.