Interstitial pneumonitis is a severe complication of juvenile dermatomyositis. We report a 4-year-old girl with juvenile dermatomyositis. Coughing, shortness of breath, and general malaise developed during steroid treatment. The histology of her lung biopsy is compatible with interstitial pneumonitis. Aggressive treatment including intravenous methylprednisolone pulse therapy, intravenous immunoglobulin, and oral cyclosporin all failed. Creatinine phosphokinase level was within the normal range during the disease course. The clinical features are discussed and the importance of a differential diagnosis of interstitial pneumonitis in patients with juvenile dermatomyositis is emphasized.