Concern exists that per case payment using Diagnosis Related Groups (DRGs) inadequately pays trauma centers. In this study, 45 Trauma Resource Groups (TRGs), an alternative patient classification system based on the Injury Severity Score and patient age, is developed and compared to 172 Diagnosis Related Groups (DRGs) that include trauma diagnoses. TRGs were developed using 1983 Maryland trauma patient hospital discharge abstracts (n= 34,702), the same source used to assign a DRG. We compared estimated TRG and DRG payments to actual charges for 17,398 trauma cases treated during 1986 at five trauma centers and 18 community hospitals in the Central Maryland Metropolitan Statistical Area. The unexpected findings of this study are that an anatomic severity-based classification of hospital trauma discharges (TRGs) does not perform as well as DRGs in: 1) explaining variations in length of stay for trauma cases, or 2) assuring an appropriate distribution of revenues to regional trauma centers and community hospitals. Solutions discussed include segregating community hospital and trauma center costs in computation of average per case rate setting, and inclusion of physiologic and mechanism of injury parameters in prospective payment classification systems to increase explained variance of resource use.