Idiopathic juvenile arthritis (IJA) is the most frequent rheumatic disease of the childhood. It is defined as a persistent arthritis, which lasts longer than 6 weeks and appears under 16 years of age, after excluding other causes of disease. We studied IJA for 5 years at the Pediatric Clinic Nr 1 in Tg. Mures (between 2001-2005). During this period there were 52 new cases diagnosed as IJA, 10 cases of systemic onset disease, 13 oligoarticular onset IJA out of which 2 developed iridocyclitis and 1 case of sacroileitis, 29 polyarticular onset IJA, out of which 5 had positive rheumatoid factor. In time 6 pacients with systemic onset disease developed polyarticular disease with severe or medium prognosis.