Juvenile idiopathic arthritis (JIA) comprises a group of heterogeneous disorders of chronic arthritis in childhood with no apparent etiology. Juvenile idiopathic arthritis is the most common pediatric rheumatic disease and is associated with significant long-term morbidity and mortality. There have been major advances in recent years in our understanding of the pathogenesis of JIA, the definition of disease control, and biological treatments for JIA. Multiple environmental and genetic factors have been linked with the onset and / or the exacerbation of JIA, including perinatal factors, viral and bacterial infections, epigenetic factors, and malnutrition. However, no single causative factor has been identified to date. As our understanding of the complex network of immune cells and inflammatory cytokines has improved, biologics have been developed to modulate the inflammatory processes. Indeed, a number of such biologics have been demonstrated effective for the treatment of JIA. Although biologic agents may alleviate the inflammation associated with JIA and prevent disability caused by joint destruction, continued and comprehensive observation is required to determine the long-term outcomes associated with such treatment.