We analyzed the clinical and laboratory features, treatment, and course of twenty-one children with systemic-onset juvenile rheumatoid arthritis (S-JRA) encountered at our institution over the past ten years. There were eleven boys and ten girls. The mean age at onset was 11.6 +/- 4.2 years. The mean duration of symptoms prior to diagnosis was 5.5 +/- 1.7 months, and the mean follow-up period was 45.7 +/- 9.5 months. The clinical and laboratory features at presentation were similar to previous reports, except that peripheral blood smear revealed toxic granulation of neutrophils in 60% of our patients. Although systemic manifestation could be readily controlled by non-steroidal anti-inflammatory drugs (NSAIDs) with or without additional steroids, nine patients suffered from chronic arthritis (duration > 6 months) requiring disease-modifying anti-rheumatic drugs (DMARDs). Of the nine children with chronic arthritis, six (67%) had a monocylic systemic course, and seven (78%) had polyarticular disease (five or more joints affected) at the disease onset. Five patients developed severe destructive polyarthritis, with persistent anemia, thrombocytosis, elevated serum C-reactive protein (CRP) levels, and marked functional limitation during follow-up. One of the five patients with severe arthritis developed systemic lupus erythromatosis after 8-year follow-up, and died of sepsis. Our study indicated significant morbidity in children with S-JRA in Taiwan.