We report the case of a 7-year-old boy with systemic onset juvenile rheumatoid arthritis (JRA) who developed macrophage activation syndrome during a period of relative remission. He presented with high-grade fever, enlarged lymph nodes, acute hepatitis, severe pancytopenia, and evidence of disseminated intravascular coagulopathy. He became severely ill, with persistent mucosal bleeding, hypovolemia, and vascular instability, and he was admitted to the intensive care unit. No response was observed to treatment with high-dose intravenous corticosteroids and blood product replacements, but the patient fully recovered after the completion of two pulses of intravenous immunoglobulin. This treatment modality may be an alternative to anti-TNF-α and cyclosporine A for a prompt response in JRA patients with this potentially fatal condition.