Idiopathic inflammatory myopathies are a group of heterogeneous, acquired systemic diseases characterized by progressive symmetrical muscle weakness, elevated serum levels of muscle enzymes, electromyographic abnormalities, and inflammatory infiltrates on muscle biopsy. Characteristic histopathologic features allow classification of idiopathic inflammatory myopathies into polymyositis, dermatomyositis, and sporadic inclusion-body myositis. These are commonly regarded as autoimmune disorders, and various autoantibodies directed to specific nuclear and cytoplasmic antigens are found. Other organs besides the muscle can be involved being the skin and lung the most frequent. Occasionally dermatomyositis and polymyositis can be associated with cancer in a paraneoplastic manner. Corticosteroids and immunosuppressive agents are the mainstay therapy, although in refractory cases biologic therapy can be used. Physical therapy can not be forgotten.