['Parenteral nutrition (PN) is often used in severely injured patients when caloric goals are not achieved enterally. The purpose of this study is to determine whether early administration of parenteral nutrition is associated with an increased risk for infection after severe injury.', 'Retrospective cohort study of severely injured blunt trauma patients enrolled from eight trauma centers participating in the "Inflammation and the Host Response to Injury" (Glue Grant) study. We compared patients receiving PN within 7 days after injury with a control group that did not receive early PN. We then focused on patients who tolerated at least some enteral nutrition (EN) during the first week and evaluated the potential influence of supplemental PN on outcomes in this "enteral tolerant" subgroup. Primary outcomes included occurrence of a nosocomial infection after the first postinjury week. Secondary outcomes included type of infection and hospital mortality.', 'Of 567 patients enrolled, 95 (17%) received early PN. Early PN use was associated with a greater risk of nosocomial infection (relative risk [RR] = 2.1; 95% CI, 1.6 to 2.6; p < 0.001). In the enteral-tolerant subgroup (n = 249), early PN was also associated with an increase in nosocomial infections (RR = 1.6; 95% CI, 1.2 to 2.1; p = 0.005) in part because of an increased risk of bloodstream infection (RR = 2.8; 95% CI, 1.5 to 5.3; p = 0.002). Mortality tended to be higher in patients receiving additional EN and PN versus EN alone (RR = 2.3; 95% CI, 1.0 to 5.2; p = 0.06).'] Is early supplemental parenteral nutrition associated with increased infectious complications in critically ill trauma patients?