BACKGROUND: Prior studies have demonstrated that transfusion of older stored blood is associated with an increased risk of multiple organ failure, infection, and death. These reports were primarily comprised of severely injured patients, and it remains unknown whether this phenomenon is observed in relatively less injured patients. The purpose of this study was to evaluate the association between the age of stored blood and the morbidity and mortality in a mild to moderately injured patient cohort. METHODS: Blunt trauma patients with Injury Severity Score < 25 admitted to a Trauma Intensive Care Unit during 7.5 years who received no blood during the first 48 hours of hospitalization were selected for inclusion. Patients who died within 48 hours of admission were excluded from analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for the association between morbidity or mortality and the age and amount of blood transfused ( > 48 hours postadmission), adjusted for age, sex, injury severity, thoracic injury, mechanical ventilation, and transfusion volume. RESULTS: During 7.5 years, 1,624 patients met the study criteria. The mean Injury Severity Score was 14.4. Receipt of blood stored beyond 2 weeks was associated with mortality (OR 1.12 [CI 1.02-1.23]), renal failure (OR 1.18 [CI 1.07-1.29] ), and pneumonia (OR 1.10 [CI 1.04-1.17]). No such associations were identified, however, concerning the transfusion of blood with a lesser storage age. CONCLUSION: In a mild to moderately injured intensive care unit patient cohort, the receipt of blood stored beyond 2 weeks was independently associated with mortality, renal failure, and pneumonia. The deleterious effect of older blood on patient outcome does not appear to be limited to the severely injured.