['To establish the prevalence of the risk of undernutrition, using criteria similar to those used by the Malnutrition Advisory Group (MAG), in people aged 65 y and over, and to identify relationships between risk of undernutrition and health and demographic characteristics.', 'A cross-sectional nationally representative sample of free-living and institutionalized older people in the UK (65 y of age and over). Secondary analysis of the National Diet and Nutrition Survey based on 1368 people aged 65 y and over.', 'About 14% (21% in those living in institutions) were at medium or high risk of undernutrition based on a composite measure of low body mass index and recent reported weight loss. Having a long-standing illness was associated with a statistically significantly increased risk of undernutrition (odds ratio: men 2.34, 95% CI 1.20-4.58; women 2.98; 1.58-5.62). The risk of undernutrition increased: in women reporting bad or very bad health status; in men living in northern England and Scotland; for those aged 85 y and older; for those hospitalized in the last year, and those living in an institution. Lower consumption of energy, meat products or fruit and vegetables and lower blood measures of zinc, vitamins A, D, E and C were associated with statistically significantly increased risk of undernutrition.'] Is prevalence of risk of undernutrition associated with poor health status in older people in the UK?