Juvenile Idiopathic Arthritis (JIA) is a disorder of unknown cause characterized by chronic inflammation of the joints and other organs. It affects about 1 in a 1000 Canadian children and if untreated it can produce lifelong disability. The Canadian Alliance of Pediatric Rheumatology Investigators (CAPRI) includes most pediatric rheumatologists in Canada. They have successfully collaborated for the past 20 years producing groundbreaking research on the modern course and outcomes of JIA. The CAPRI JIA Registry is an ongoing universal registry of Canadian children with JIA that collects longitudinal data on disease course, outcomes and adverse events to inform healthcare decisions and to gain new insights into the disease and its treatment.