Since its introduction in 1999 etanercept, a tumor necrosis-alpha blocker, has become a very important treatment option for Juvenile Idiopathic Arthritis (JIA) patients refractory to synthetic Disease Modifying Anti-Rheumatic Drugs. JIA is on of the most common auto-immune diseases in childhood; prevalence is one in 1,000 children. JIA can result in irreversible changes in cartilage and bone and long-term functional impairment and chronic pain. In the Arthritis and Biologicals in Children (ABC) project, all Dutch JIA patients who use or have used etanercept are included. Main aim of the project was to describe long-term effectiveness and safety of etanercept for patients with JIA. Methodology of data collection through the web-based ABC-register and the digitalized Childhood Health Assessment Questionnaire are described. Results showed that the greatest improvement in the disease course occurred in the first 3 months of treatment with etanercept, for the majority of patients this improvement was sustained (up to 75 months); 53 (36%) of all patients met the remission criteria. Adverse events rate was low. In addition, major improvements in health-related quality of life (HRQoL) were shown on both the disease specific as on generic HRQoL outcomes. Considering these improvements in the disease course and HRQoL, the high costs of etanercept therapy are justifiable, since the JIA patients treated were previously refractory to conventional treatment, and were at risk for long-time disability and pain. Etanercept treatment strategies were evaluated and showed that the double dose of 0.8 mg/kg once weekly is as effective as the usual dose of 0.4 mg/kg twice weekly to induce and retain remission in JIA patients. Successfully treated JIA patients should meet the clinical remission criteria on etanercept for at least 1.5 years before discontinuation. Patients who fail to meet response criteria at 3 months of treatment, should continue etanercept till at least 6 months, before switching to other therapies. Etanercept is ...