The definition of sarcopenia continues to evolve, from an observational phenomenon to a differential diagnostic approach. Clinical relevance for sarcopenia is defined by a loss in lean muscle mass and impairment of functional status. A therapeutic approach to the loss of skeletal muscle mass and strength in older persons depends on correct classification. The term sarcopenia is reserved for age-related decline in muscle mass not attributable to the presence of proinflammatory cytokines. For persons with sarcopenia, the primary intervention should include resistance exercise. An improvement in muscle mass and strength has been demonstrated with resistance exercise, even in the very old. Targeting the hormonal changes with aging is an attractive intervention. However, testosterone replacement in elderly hypogonadal men has demonstrated only modest increases in muscle mass and strength. Administration of growth hormone in pharmacologic doses increases muscle mass but not muscle strength. Nutritional therapy is promising, but the effects in clinical trials have been small.