JuMBO is a prospective observational cohort study and represents the follow-up register of the national juvenile idiopathic arthritis (JIA) biologic register "BiKeR". It was set up to assess the safety and effectiveness of biologic and non-biologic disease modifying antirheumatic drugs (DMARDs) in adult subjects with JIA under real life conditions in 2007.Subjects observed in JuMBO were formerly included in BiKeR, have reached 18 years of age or have left paediatric care, and were ever treated with a biologic and/or non-biologic DMARD. Each subject is followed prospectively for up to 10 years after starting with a specific DMARD. Patients are half-yearly assessed by a short clinical record and a patient questionnaire. The measuring instruments comprise among others the following parameters: number of swollen and/or tender joints, physician's overall assessment of disease activity, patient’s global assessment of overall well-being, laboratory values (CrP, ESR), functional status (Health Assessment Questionnaire), patient’s assessment of pain, morning stiffness, quality of life (SF-36, EuroQoL), hospitalizations, costs, mortality, time on biologic or MTX therapy, and reasons for change of treatment. Adverse events (AEs) and serious adverse events (SAEs) are recorded according to the EMA guidance “Clinical safety data management: definitions and standards for expedited reporting”, ICH Harmonized Tripartite Guideline. AEs occurring during the observation period are recorded by physicians regardless of the patients´ current treatment. In addition to physician-reported AEs, patients are asked to report health problems. Therewith, JuMBO enables the identification of important AEs and their associations with therapeutic agents. In addition, the data collected allow for describing treatment patterns of JIA in adulthood, examining long-term clinical and patient-centered outcomes, and costs of illness