Idiopathic inflammatory myopathies, polymyositis, dermatomyositis, and inclusion body myositis, are increasingly recognized to cause long-term disability in certain subsets of patients. Because these diseases are infrequent, only retrospective analysis of most treatments are available. In this article, identification of subsets of patients with different prognoses and discussion of confounding factors for increasing weakness are emphasized. The advantages and disadvantages of different therapies for myositis and for extraskeletal muscle features are also discussed.