Juvenile rheumatoid arthritis (JRA) is best defined as the condition of chronic synovitis in children. Such chronic childhood arthritis probably includes several distinct disease processes. Recognizable subgroups are systemic-onset disease (20%), rheumatoid factor-negative polyarthritis (25%), rheumatoid factor-positive polyarthritis (5%), pauciarthritis associated with antinuclear antibodies and chronic iridocyclitis (30%-35%), and pauciarthritis associated with sacroiliitis and HLA-B27 (10%-15%). Rheumatoid factor-positive polyarthritis appears to be the childhood equivalent of classic adult rheumatoid arthritis; the pauciarthritis associated with HLA B27 appears to be closely related to the spondyloarthropic diseases. Although there are no diagnostic laboratory tests, various subgroups differ in immunogenetic findings as well as in clinical appearance and prognosis. A wide variety of conditions (infectious diseases, childhood malignancies, genetic and congenital conditions, and noninflammatory musculoskeletal lesions) can mimic JRA and must be considered in the differential diagnosis. The outlook for most children with JRA is good; fewer than 20% have progressive destructive disease (generally those with rheumatoid factor-positive or systemic-onset disease). Therapy rests on the conservative use of antirheumatic drugs, active physical therapy programs, maintenance of activities, and attention to the psychosocial development of the whole child. Orthopedic surgery can be helpful, particularly in the rehabilitation of children who have suffered severe joint destruction or deformity. Combined orthodontic and oral surgery therapy can restore function and appearance for young people with the micrognathia of temporomandibular joint involvement.