Nutritional support of surgical and critically ill patients has undergone significant advances since 1936 when Studley demonstrated a direct relationship between pre-operative weight loss and operative mortality. The advent of total parenteral nutrition followed by the extraordinary progress in parenteral and enteral feedings, in addition to the increased knowledge of cellular biology and biochemistry, have allowed clinicians to treat malnutrition and improve surgical patient's outcomes. We reviewed the literature for the current status of perioperative nutrition comparing parenteral nutrition with enteral nutrition. In a surgical patient with established malnutrition, nutritional support should begin at least 7-10 days prior to surgery. Those patients in whom eating is not anticipated beyond the first five days following surgery should receive the benefits of early enteral or parenteral feeding depending on whether the gut can be used. Compared to parenteral nutrition, enteral nutrition is associated with fewer complications, a decrease in the length of hospital stay, and a favorable cost-benefit analysis. In addition, many patients may benefit from newer enteral formulations such as Immunonutrition as well as disease-specific formulations.