Nutritional therapy in the intensive care unit exerts favourable effects on morbidity and mortality. Enteral nutrition is preferable to parenteral nutrition. Only perforation or total obstruction of the gastrointestinal tract, proven mesenteric ischaemia and toxic megacolon are absolute contra-indications to enteral nutrition. Early enteral nutrition is effective in decreasing infectious complications and reducing the length of stay in the hospital. Nutrition that is enriched with specific ingredients in order to modulate the immune response is referred to as immunonutrition. The use of immunonutrition, notably in surgical intensive care patients, has a favourable effect on the incidence of infectious complications, the duration of artificial respiration and the length of hospital stay. The addition of glutamine to parenteral nutrition may reduce mortality compared to standard parenteral nutrition. Implementation of a simple feeding algorithm in the intensive care unit, with special attention for the treatment of delayed gastric emptying, is cost-effective and leads to an improvement in the nutritional parameters.