Myopathy is a convenient shorthand term meaning muscle disease or dysfunction. In other words, the myopathies are those conditions in which the patient's symptoms and signs can be attributed to a pathological process affecting either the structure of muscle fibres or their associated interstitial tissues, or to disturbance of the biochemical or electrophysiological function of those fibres. Myopathies are rare in all age ranges. They may be inherited or acquired. Onset of inherited myopathies in elderly people, not surprisingly, is uncommon, but some of these diseases are asymptomatic, or cause such minor symptoms that their significance is not appreciated by the patient, and thus they may not be recognized until late on in life. Their recognition may have implications for other, younger, family members. Many of the acquired myopathies afflicting older people are treatable, but the commonest, inclusion body myositis, is not, and incorrect diagnosis and inappropriate use of steroids may compound morbidity.