Sarcopenia refers to the loss of muscle mass and strength seen with advancing age. The pathophysiology is multifactorial, with loss of muscle satellite cells, changes in hormonal systems, chronic inflammation, oxidative stress and anabolic resistance to protein utilisation all implicated. Older age, female sex and immobility are important risk factors. Sarcopenia is clinically important as it is a major risk factor for physical frailty, falls, prolonged hospitalisation, dependency and earlier death. Diagnosis requires evidence of reduced muscle mass measured by handgrip strength or walk speed, together with evidence of low muscle mass, measured by one of a variety of techniques such as bioimpedance analysis or dual X-ray absorptiometry. Resistance training is the only intervention of proven efficacy to treat sarcopenia, but a range of nutritional and pharmacological interventions are under test, including myostatin inhibitors, leucine and protein supplementation, angiotensin-converting enzyme inhibitors and allopurinol.