The severe hypermetabolism and hypercatabolism seen in patients with severe head injuries results in malnutrition that occurs very rapidly and can cause impaired healing and an increased tendency to infection and multiple organ failure. Thus, early adequate nutritional support plays a role in functional outcome. Total enteral nutrition (TEN) is preferred over total parenteral nutrition (TPN), but TPN should be supplied promptly while increasing TEN to a goal of at least 25 to 35 nonprotein kcal/kg/d and 2.0 to 2.5 g protein/kg/d. Nutritional formulas high in branched chain amino acids, glutamine, arginine, vitamins E and C, and zinc may also have some advantages. Growth hormone may improve anabolism. Hyperglycemia, especially glucose levels exceeding 200 mg/dL, must be prevented and/or treated promptly with insulin or decreased glucose intake. Careful monitoring with indirect calorimetry and nitrogen balance studies should help prevent inadequate protein or excessive carbohydrate intake.