The prevalence of undernutrition in older individuals, living independently in a community setting, or living in a supported setting, is considerable. The negative health effects of undernutrition are wide ranging, with implications for quality of life (QOL), well-being and general health, through to the individual's ability to recovery from acute disease. There are a number of key measures that indicate both nutritional status and the effectiveness of any intervention. These include conventional anthropometric and biochemical measures of nutrient status, as well as measures of QOL, well-being and depression. The latter have huge importance to the life of the individual, and to date appear to have undergone only preliminary investigation. This review suggests that the efficacy of interventions to address undernutrition and improve health in older people living in a variety of settings is highly variable, and that considerable opportunities for research in this area exist.