The immunologic competence of 12 patients with advanced and fulminating prosthetic graft infections was studied. Critical deficiencies were noted in the immune status of all the patients. Enhancement of immune responses with accelerated recovery occurred in 8 of the 12 patients who received total parenteral nutritional support. The four patients who exhibited anergy and were not given the benefits of supplemental nutrition endured a prolonged convalescence, and two subsequently died. This study brought to our attention not only the prevalence of depressed host resistance in these critically ill individuals with advanced prosthetic graft injections but also the benefits of adjunctive parenteral nutritional support in combination with the more conventional modes of therapy, including antibiotics, surgical removal of the septic nidus, and bypass to restore arterial continuity.