AIM To ascertain criteria of aggressive course of juvenile rheumatoid arthritis (JRA) during 6-12 months since the disease onset, to measure the rate of destruction progression, to formulate indications for conduction of early immunosuppressive therapy. MATERIALS AND METHODS The study included 30 patients (21 girls and 9 boys) aged 4-15 years with classic JRA. 25 children (76.2%) had systemic, 5 children--articular disease (23.8%). RESULTS 50% and 20% of the examinees got the disease before they reached the age of 5 years and in puberty, respectively. Severe systemic disease in the debute was registered in 83.3% of patients, 16.7% developed primarily articular JRA. For 1 year the disease transformed into generalized and polyarticular in 43.3% and 56.7% of patients, respectively. Its activity reached the third degree in all the patients. IgG levels exceeded the age standards 1.5 times. Articular dysfunction occurred in 100% of the cases. Destruction in the joints was recorded in 37% and 92.5% of patients after 1 and 2 years of the disease, respectively. CONCLUSION Early or in prepuberty, puberty onset of JRA, systemic variants of the debute, debute by classical seropositive RA without systemic symptoms, fast appearance of symmetric, generalized joint lesions, recurrent course with high ESR, C-reactive protein, IgG, growing joint functional insufficiency within the first year of the disease may severe criteria of aggressive course of RA in children. RESULTS The presence of the above markers in RA patients is indication for administration of the disease-controlling drugs within the first 12 months before development of anatomic destruction and the patients' invalidation.