The incidence of denutrition in hospitalized patients is high. A relation exists between morbidity and the altered nutritional status. Parenteral nutrition is one way to preserve or to restore the nutritional equilibrium. Certain risks of the method (septicemia, hyperglycemia, hyperosmolarity) are well known and can easily be prevented; other metabolic effects have recently been published. The indication for parenteral nutrition, the proper timing, the total amount and the proportion of the nutrients must be carefully analysed for each individual patient. It seems essential to define objective parameters to determine the nutritional status of the patient as well as the effect of the applied nutritional therapy.