A satisfactory classification of arthritis in childhood has still to be defined, and a system that can facilitate communication among physicians has been proposed by an international committee. The immunopathogenesis of the diseases that are encompassed by the term juvenile rheumatoid arthritis is complex, and many studies have investigated the role of genetic and cytokine balance abnormalities. HLA associations have been confirmed in multiple series, and there is evidence that non-major histocompatibility complex genes might also contribute to disease pathogenesis. Recent studies have added knowledge to the diverse clinical features of the disease, including joint distribution at presentation, association with Turner syndrome, presence of arthritis mutilans, and alterations in mandibulofacial development. Medical treatment remains a challenge. For cases recalcitrant to conventional therapy autologous hemopoietic stem-cell transplantation has been attempted; the risks of this procedure must however be carefully balanced in individual patients.