Objectives-To determine incidence of malnutrition among patients on admission to hospital, to monitor their changes in nutritional status during stay, and to determine awareness of nutrition in different clinical units.Design-Prospective study of consecutive admissions.Setting-Acute teaching hospital.Subjects-500 patients admitted to hospital: 100 each from general surgery, general medicine, respiratory medicine, orthopaedic surgery, and medicine for the elderly.Main outcome measures-Nutritional status of patients on admission and reassessment on discharge, review of case notes for information about nutritional status.Results-On admission, 200 of the 500 patients were undernourished (body mass index less than 20) and 34% were overweight (body mass index >25). The 112 patients reassessed on discharge had mean weight loss of 5.4%, with greatest weight loss in those initially most undernourished. But the 10 patients referred for nutritional support showed mean weight gain of 7.9%. Review of case notes revealed that, of the 200 undernourished patients, only 96 had any nutritional information documented.Conclusion-Malnutrition remains a largely unrecognised problem in hospital and highlights the need for education on clinical nutrition.