Juvenile chronic arthritis encompasses a heterogeneous spectrum of diseases that all include at least one persistent inflammatory arthritis. Its definition is based upon clinical criteria after exclusion of a long list of differential diagnoses. Three main types of onset are generally considered according to the clinical features during the first 3 months of evolution: systemic (20%), oligoarticular (50%), polyarticular (30%). Systemic forms present with acute general symptoms and a wide variety of articular features, from polyarthritis to isolated arthralgias. Oligoarticular forms involve 4 or fewer joints and are often complicated with iridocyclitis especially in case of positive antinuclear antibodies in the serum. Polyarticular forms involve at least 5 joints and include the presence of rheumatoid factor in the serum in 10% of cases. The clinical course of juvenile chronic arthritis is unpredictable and the reliability of the current classification is limited by taking into account only the first 3 months of evolution.