We present a review of the criteria for the classification of juvenile arthritides. Historical aspects, the present situation and proposals for new criteria are outlined. The most commonly used classification criteria today are the European juvenile chronic arthritis criteria (JCA), the European League Against Rheumatism (EULAR) criteria, and the American juvenile rheumatoid arthritis (JRA), the American Rheumatoid Association (ARA) criteria. They differ in nomenclature and have different inclusion and exclusion demands. This has made it difficult to compare studies using different criteria. Neither of them can define homogeneous subgroups of disease. The most recent proposal for new classification criteria of juvenile arthritides is that of the International League Against Rheumatism, ILAR. They are primarily designed to define homogeneous subgroups of disease. The goal is also to obtain an international consensus. Advantages and disadvantages are discussed in this article. The criteria have not yet been validated, and should not be used by clinicians until they have been approved by the international scientific society. We also present guidelines recommended for the classification of juvenile arthritis in Norway today. We recommend using the term juvenile arthritis. Disease duration of arthritis must be at least six weeks. A diagnosis of arthritis should not be made on painful and restricted joint movement alone, as is the case in both the EULAR and ARA criteria today, but at least be based on definite swelling of joints verified by either clinical examination and/or by imaging techniques such as ultrasound, X-ray or EMR.