Sarcopaenia, or decreased muscle mass, has been the subject of a large quantity of recent literature in both medical and surgical disciplines. It has been shown, as outlined below, to be of great prognostic importance, and also may be used in certain circumstances to guide treatment. The greatest volume of research into this topic is in oncological surgical populations, in whom the prevalence of sarcopaenia has been shown to be high. However it is being increasingly studied in other patient groups. Interest in using sarcopaenia as an objective and potentially modifiable marker of frailty is increasing, especially with regards to pre-operative risk stratification and amelioration. In this review we consider the current literature regarding the cause and effect of sarcopaenia, the methods by which it may be identified and the potential ways in which it may be treated, in the interest of improving outcomes for surgical patients.