Inflammatory myopathies are comprised of three major subsets, polymyositis, dermatomyositis and inclusion body myositis. Although their etiology is unclear, each group retains its characteristic clinical, immunopathologic features. In polymyositis, a CD8+ T-cell mediated cytotoxicity against muscle fibers has emerged as the main pathologic event, whereas in dermatomyositis complement-mediated injury by antibody may be the primary pathology. There has been several reports on polymyositis internationally but we could find only a few reports in Korea. We report here a 8-year old female patient admitted with a stuporous mentality. After coughing and fever for 3 days, she got myalgia, abruptly developed gross hematuria and dyspnea. After admission, she showed weak self respiration and exclussively elevated muscle enzyme in blood chemistry. In muscle biopsy, lymphocytic infiltrations were found in the fascicles without endomysial fibrosis and these lymphocytes were composed of T lymphocytes on immunohistochemical stain. She received two infusions of intravenous immunoglobulin(1g/kg/day), and showed dramatic improvement in symptoms and signs.