OBJECTIVE. This study examines the cost of providing trauma services in trauma centers organized by publicly administered trauma systems, compared to hospitals not part of a formal trauma system. DATA SOURCES AND STUDY SETTING. Secondary administrative discharge abstracts for a national sample of severely injured trauma patients in 44 trauma centers and 60 matched control hospitals for the year 1987 were used. STUDY DESIGN. Retrospective univariate and multivariate analyses were conducted to examine the impact of formal trauma systems and trauma center designation on the costs of treating trauma patients. Key dependent variables included length of stay, charge per day per patient, and charge per hospital stay. Key impact variables were type of trauma system and level of trauma designation. Control variables included patient, hospital, and community characteristics. DATA COLLECTION/EXTRACTION METHODS. Data were selected for hospitals based on (1) a large national hospital discharge database, the Hospital Cost and Utilization Project, 1980-1987 (HCUP-2) and (2) a special survey of trauma systems and trauma designation undertaken by the Hospital Research and Educational Trust of the American Hospital Association. PRINCIPAL FINDINGS. The results show that publicly designated Level I trauma centers, which are the focal point of most trauma systems, have the highest charge per case, the highest average charge per day, and similar or longer average lengths of stay than other hospitals. These findings persist after controlling for patient injury and health status, and for demographic characteristics and hospital and community characteristics. CONCLUSIONS. Prior research shows that severely injured trauma patients have greater chances of survival when treated in specialized trauma centers. However, findings here should be of concern to the many states developing trauma systems since the high costs of Level I centers support limiting the number of centers designated at this level and/or reconsidering the requirements placed on these centers.