The definition and management of "early arthritis" in children differ from those in adults because juvenile idiopathic arthritis (JIA) is markedly different from adult rheumatoid arthritis. Since a significant proportion of patients with JIA develop articular damage and enter adult life with persistently active disease, it is important to predict early in the disease course the long-term outcome in order to tailor treatment to the risk of disability. Over the past 3 decades a number of studies have evaluated the long-term outcome of cohorts of patients with JIA and some of them have also attempted to identify early prognostic factors. In summary, greater severity/extension of arthritis at onset, symmetric disease, precocious hip/wrist involvement, the presence of rheumatoid factor, and prolonged active disease were the best predictors of a poor outcome. Specific correlates for systemic JIA were persistent systemic features and thrombocytosis at 6 months following presentation, whereas joint symmetry and a higher erythrocyte sedimentation rate at onset were associated with a more severe course in oligoarticular JIA. However, although data is accumulating on prognostic factors in JIA, prediction of long-term outcome in the first few months remains difficult. To better define prognostic factors in future analyses, a considerable effort should be made to increase standardization among studies. Furthermore, a radiographic scoring system and a set of remission criteria specific for JIA should be developed.