Until the age of biotechnology, treatment options for children and adolescents with severe arthritis, inflammatory bowel diseases and other serious diseases with chronic inflammation were limited. Advances in understanding the pathophysiology of the inflammatory responses have led to the development of a new class of medications that are capable of inhibiting selectively the principal mediators of inflammation and tissue damage. The introduction of these new immunomodulators, which are collectively termed biologics, has opened a new era in the treatment of inflammatory diseases. Recent reports however suggest unexpected increases in adverse - or serious events -associated with the use of these biologics. PHARMACHILD aims to detect, assess and understand long term and short term side effects of the use of biologics by studying the pharmacovigilance in a large international cohort of patients with Juvenile Idiopathic Arthritis (children and young adults) in order to support regulatory decisions on marketing authorizations for these products.There is a clear need for a study that will enable the promotion of more effective and safer use of biologics in JIA as children and young adolescents represent an especially vulnerable patient group, JIA is the most common chronic disease of childhood treated with biologics, and data available from adults cannot be extrapolated to children. PHARMACHILD brings together leading European scientists in the field of infectious diseases, immunity, inflammation and oncology. Our network combines resources from international organizations and existing national registries. This combination will enable us to achieve the critical mass (in terms of expertise and resources) to identify the risk factors for developing adverse events, to elucidate the mechanisms involved in the adverse events (such as latent infection reactivation) and to develop methodologies for screening and predicting patients at risk.