BACKGROUND: Although injured persons presenting to nontertiary hospitals are routinely transferred for further care, it is unknown whether there is an outcome benefit associated with this practice. We sought to assess whether the transfer of injured patients from nontertiary hospital emergency departments (EDs) is associated with improved survival. METHODS: This was a retrospective cohort analysis of all consecutive injured children and adults meeting state trauma criteria, presenting to 1 of 42 nontertiary hospital EDs (primarily rural) and requiring either admission or transfer (n = 10,176) from January 1998 through December 2003. Higher level of care transfer was defined as interhospital transfer from the ED to one of six Level I or II trauma centers. Propensity scores were used to adjust for the known nonrandom selection of patients for higher level of care transfer. The outcome measure was inhospital mortality. RESULTS: There were 10,176 trauma patients who presented to nontertiary hospital EDs and were included in the analysis, of which 3,785 (37%) were transferred to a tertiary hospital from the ED. Transfer patients had higher unadjusted mortality (odds ratio [OR] 2.83, 95% confidence interval [CI] 2.06-3.89). After adjusting for the propensity to be transferred, transfer from the ED to a tertiary hospital was associated with a reduction in mortality (OR 0.67, 95% CI 0.48-0.94), which was strongest among patients transferred to Level I hospitals (OR 0.62, 95% CI 0.40-0.95). There was no measurable benefit for patients transferred to Level II hospitals (OR 0.82, 95% CI 0.47-1.43). CONCLUSIONS: After adjusting for injury severity and the nonrandom selection of patients for transfer, trauma patients transferred from nontertiary EDs to major trauma centers had lower inhospital mortality than patients remaining in nontrauma hospitals. Recognition and early transfer of at-risk rural trauma patients may improve survival in a regionalized trauma system.