Dr. Stanley Dudrick invented total parenteral nutrition in 1968, providing a desperately needed therapy to those patients who could not eat. It has since saved thousands of patients worldwide. Nutrition interventions (NI) in surgical/trauma and critically ill patients have evolved dramatically during the last 20 years from a supportive therapy to a clear therapeutic role. Like any other form of therapy, NI will benefit patients when adequately indicated and prescribed. NI, however, may cause significant side effects and harm when poorly ordered. This article reviews the indications for the prescription of the different forms of NI available to the clinician caring for the surgical patient.