Malnutrition is frequent in geriatric patients: it affects 30 to 60% of elderly residents of institutions and 30 to 70% of patients admitted for short-term hospitalization. Malnutrition is a risk factor for developing pressure sores, and patients with them are more often and more severely malnourished than patients without them. In elderly subjects, multiple and interlinked factors may trigger or aggravate malnutrition; they may be physical, psychological or social and may be worsened by drugs and some diets. Malnutrition has been recognized as a risk factor for the onset and perpetuation of pressure sores. Of the dietary factors, protein intake seems most important. A low body mass index (BMI), low serum albumin, and weight loss are associated with an increased risk of pressure sores. A physician observing pressure sores must conduct a nutritional assessment, using clinical and laboratory screening tools. The criteria for malnutrition in elderly subjects are weight loss > or =5% in 3 months or > or =10% in 6 months, BMI<21 kg/m(2), serum albumin<35 g/L or a MNA (Mini Nutritional Assessment) score<17. Any one of these criteria is a sufficient basis for a diagnosis of malnutrition. Nutritional management is part of the prevention and treatment of pressure sores in geriatric medicine. It must be adapted for each patient. The recommended calorie intake in malnourished patients at risk of or with pressure sores is 30-40 kcal/kg/d, with 1.2-1.5 g of proteins/kg/d.