Background: Injury is the leading cause of death for persons aged 1-44 years in the United States. Injuries have a substantial economic cost. For that reason, regional systems of trauma care in which the more acutely injured patients are transported to Level-I (L-I) trauma centers (TCs) has been widely advocated. However, the cost of TC care is high, raising questions about the value of such an approach. Objectives: To study L-I TC effectiveness and study return-to-work (RTW) outcomes. Research Design: Using data from National Study on the Costs and Outcomes of Trauma, the authors address the issue of selection bias by comparing naive estimates to matching techniques, as well as to nonlinear instrumental variable models (2SRI) and bivariate probit estimators. Subjects: Individuals ages 18-64 who were mainly working before traumatic injury. Patients selected for the study were treated at 69 hospitals located in 12 states in the United States. N = 1790. Measures: Treatment is binary indicator on whether treated at L-I TC. Outcome is binary indicator on whether returned to work within 3 months after injury. Covariates include: demographics, pre-injury characteristics (job, health and insurance status), injury descriptors, other income sources, etc. Results: Across all models that control for unobserved factors, the authors find that L-I TC treatment is positively associated with RTW within 3 months after injury. The estimated average marginal effect of treatment on the probability of RTW ranges from 23 to 38 percentage points. Conclusions: Benefits of L-I TC care extend beyond mortality and morbidity. (Contains 6 tables, 2 graphs, and 20 notes.)