It can be expected that every fifth patient in an internal medical ward in our hospitals is malnourished. Reasons for this are consuming underlying diseases as well as psychological and social factors. The association of malnutrition and hypoalbuminemia is a marker of poor prognosis; malnutrition associated with hypoalbuminemia has also been named `protein malnutrition`. However, this term is misleading and `dysproteinemic malnutrition` would be more appropriate, because hypoalbuminemia is usually not caused by protein malnutrition but rather by an underlying severe illness. The nutritional state should be assessed in all patients with suspected malnutrition; not only body composition but also body function should be determined. Elderly patients have an increased prevalence of malnutrition; among individual micronutrients vitamin D, B12 and B6 in particular are frequently diminished. Nutritional therapy should be a component of all comprehensive treatment programmes for diseases which may lead to malnutrition.