Muscle weakness and muscle fatigue are the most common manifestations in patients with idiopathic inflammatory myopathies (ie, myositis), but other organs are frequently involved such as skin, lungs, joints, and the heart. These could occur before, simultaneously with, or after the onset of muscle symptoms. One tool to structure outcome measure is the International Classification of Functioning, Disability, and Health. Measures of "disability" can be divided into impairment and activity limitation/participation restriction. Most of the available outcome measures for myositis could be classified as measures of impairment, such as muscle strength, serum levels of muscle enzymes, and pulmonary function tests. Measures of activity limitation/participation restriction are also important, such as the myositis activities profile, the visual analog scale to assess impact on general well-being, and the generic short form-36 to capture impact on health-related quality of life.