Background & aims: One in four hospital patients in the UK are estimated to be affected by 'hospital malnutrition' (under-nutrition). There is a need for robust epidemiological data relating to the frequency, distribution and determinants of this clinical problem of public health importance. This review aims to undertake a narrative synthesis of data on the descriptive epidemiology of under-nutrition, and to address some of the methodological limitations. Methods: A methodical review of literature was undertaken, tracking the reported prevalence and incidence of under-nutrition in hospital, in the UK, since 1994. Results: The 16 articles retrieved and reviewed demonstrate that nutrition in hospital is a long standing problem in UK hospitals and care homes. The existing literature is comprised mainly of cross-sectional surveys describing the prevalence of under-nutrition in hospital which ranges from 11 to 45%. There is considerable heterogeneity in the published literature on hospital malnutrition (under-nutrition) and very few studies either measure or have estimated incidence. Conclusions: Under-nutrition in hospital continues to be under-addressed, yet a major public health problem in the UK. Defining the descriptive epidemiology of this problem is one of the first steps towards understanding its aetiology or planning and evaluating appropriate prevention or treatment strategies. © 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism.