Background: Combined trauma and burn injuries are uncommon and seldom studied. There is a presumption that these patients fare worse than their trauma- and burn-only counterparts, but the mortality risk has not been quantified. Methods: This was a retrospective cohort study using the 1994 to 2002 National Trauma Data Bank. Trauma- and burn-only patients were categorized according to Injury Severity Score (ISS) and burn severity (percentage body surface area burned [BSAB]), respectively, and combined trauma-burn patients were similarly categorized. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated comparing combined trauma-burn mortality to trauma-only and burn-only patients by corresponding trauma or burn severity. RRs were adjusted for age, gender, and ISS or burn severity. Results: Compared with minor trauma-only patients (ISS of 1-15), patients with minor trauma, when combined with burn injury, had significantly increased mortality (RR, 4.04; 95% CI, 3.51-4.66). Similarly, relative to minor burn-only patients (BSAB of 1-25%), combined trauma-burn patients with minor burns (RR, 5.00; 95% CI, 3.54-7.06) had significantly increased mortality. For combined trauma-burn patients with more severe burns or trauma, small but significant increased mortality risks were seen relative to major trauma-only patients (ISS of 26+; RR, 1.26; 95% CI, 1.05-1.51) and major burn-only patients (BSAB of 76+; RR, 1.45; 95% CI, 1.15-1.82). Conclusion: The large increased risk of death for those with combined minor injuries is of clinical interest because the majority of combined patients fall into this category. Future research should characterize specific causes and types of injury of increased mortality in the patient with combined injuries.