A new methodology is presented for evaluating the extent to which patients within regionalized systems of trauma care are treated at the appropriate hospitals. Criteria are proposed for retrospectively classifying trauma patients as to whether they should have been treated at a trauma center. The criteria were developed by a panel of nationally recognized trauma experts and are based on the age of the patient and the type and AIS severity of injuries sustained. The criteria were then applied to uniformly collected data available for all trauma discharges in 1988 from acute care hospitals in a state with a well developed system of regionalized trauma care. According to the criteria, 19% of all trauma discharges in 1988 should have been treated at a trauma centers. Of those who should have been treated at a trauma center according to criteria, 66% actually received treatment at a center. Of those who were classified not to have required care at a trauma center, 62% actually were treated at non-trauma center hospitals. The congruence between where patients should have been treated and the actual level of hospital care received varied by the type and severity of the traumatic injuries sustained. The results of the analysis provide insights into the characteristics of trauma patients at higher risk of not getting the appropriate level of trauma care and should assist in improving guidelines for triage and transfer within a regionalized system of care.