Artificial nutrition (AN) has become an essential part of traumatised and surgical patient care. The main indications for AN are severe undernutrition and hypermetabolism, which are important causes of immunosuppression. Total parenteral nutrition has proved to be as beneficial in the perioperative period only in malnourished subjects. In contrast, overfeeding may cause detrimental sequelae with an increase in postoperative complications. Experimental and clinical trials have clearly shown that the administration of nutrients via the enteral route versus the parenteral one has several advantages, including improved local and systemic immune response and gut barrier function with the subsequent reduction of septic morbidity. Preliminary data in traumatised and surgical patients have shown further immunological and clinical advantages when the composition of the enteral solutions has been enriched with specific nutrients capable of enhancing the host defence mechanisms. The most important are arginine, n-3 fatty acids, RNA, and glutamine.