Nutrition support plays an important role in the management of nutritional deficiencies in properly selected critically ill patients. A full nutritional assessment allows the calculation of appropriate feeding goals. The route of feeding, enteral or parenteral, is determined by the presence or absence of a functioning intestine and hemodynamic status of the patient. The specific roles of carbohydrates, fats, and protein need to be considered in order to prevent overfeeding and other complications. The efficacy of certain disease-specific enteral formulas has been demonstrated in clinical trials, however, careful cost-benefit analyses are required.