Juvenile rheumatoid arthritis (JRA) is the most common arthritis of childhood. It represents a group of disorders that share the clinical manifestation of chronic joint inflammation. The etiology is unknown, and the genetic component is complex, making clear distinctions between the various subtype is also difficult. As a result, the various sets of classification criteria that have been recognized have different benefits and limitations. A new nomenclature, Juvenile Idiopathic Arthritis (JIA), is being increasingly used in order to define the subgroups better.