THE PURPOSE OF THE STUDY was to evaluate the peculiarities of the clinical features, laboratory parameters and tactics of treatment in juvenile idiopatic systematic arthritis.A retrospective data review of 41 children (26 boys and 15 girls) who underwent treatment for systemic arthritis (according to ILAR criteria) in our institution between 1992 and 2002 was performed.The disease started with fever of unknown origin in all cases. In 73% of patients it lasted longer than one month, in 54% fever was with twice daily spikers in the morning and in the evening. The rash during the rise of temperature appeared in 49%, in most cases (70%) there was a maculo-papular rash. Lymphadenopathy and serositis were observed in 32%, hepatomegaly in 29%, and splenomegaly in 24%. Arthritis coincided with the fever in 29% of patients, in majority of cases it was progressing to a severe persistent arthritis after the systematic phase. There was no specific laboratory findings: neutrophilic leucocytosis was found in 73%, anemia - in 80.5%, trombocytosis - in 36.6%, elevated CRP - in 63.4%, dysproteinemia - in 79% of patients. Antinuclear factors were absent in all examined children. For all patients intravenous methylprednisolone pulses have been administered (10-22 mg/kg/infusion). Prednisolone was also continued orally (1-2 mg/kg/day). 24.4% of patients required in addition immunosupressive agents such as methotrexate, azathioprine and cyclophosphamide.Puls-therapy of methylprednisolone is a safe and sufficiently effective method of treatment in most cases of the systematic juvenile arthritis.