Background: Accurate economic data are fundamental for improving current funding models and ultimately in promoting the efficient delivery of services. The financial burden of a high trauma casemix to designated trauma centres in Australia has not been previously determined, and there is some evidence that the episode funding model used in Australia results in the underfunding of trauma. Aim: To describe the costs of acute trauma admissions in trauma centres, identify predictors of higher treatment costs and cost variance in New South Wales (NSW), Australia. Materials and methods: Data linkage of admitted trauma patient and financial data provided by 12 Level 1 NSW trauma centres for the 08/09 financial year was performed. Demographic, injury details and injury scores were obtained from trauma registries. Individual patient general ledger costs (actual trauma patient costs), Australian Refined Diagnostic Related Groups (AR-DRG) and state-wide average costs (which form the basis of funding) were obtained. The actual costs incurred by the hospital were then compared with the state-wide AR-DRG average costs. Multivariable multiple linear regression was used for identifying predictors of costs. Results: There were 17,522 patients, the average per patient cost was $10,603 and the median was $4628 (interquartile range: $2179-10,148). The actual costs incurred by trauma centres were on average $134 per bed day above AR-DRG costs-determined costs. Falls, road trauma and violence were the highest causes of total cost. Motor cyclists and pedestrians had higher median costs than motor vehicle occupants. As a result of greater numbers, patients with minor injury had comparable total costs with those generated by patients with severe injury. However the median cost of severely injured patients was nearly four times greater. The count of body regions injured, sex, length of stay, serious traumatic brain injury and admission to the Intensive Care Unit were significantly associated with increased costs (p < 0.001). Conclusion: This multicentre trauma costing study demonstrated the feasibility of trauma registry and financial data linkage. Discrepancies between the observed costs of care in these 12 trauma centres and the NSW average AR-DRG costs suggest that trauma care is currently underfunded in NSW.