background: Routine laboratory evaluation of preoperative patients has not been shown to be cost effective when a detailed history and physical examination are performed. However, since such a detailed history is not possible in trauma patients, the time-honored approach has been for laboratory evaluation to be protocol driven. The cost-benefit ratio of this practice has never been evaluated.methods: Trauma patients who underwent routine laboratory evaluation (n = 552; group I) were compared with patients who had laboratory evaluation based on clinical need (n = 603; group II). A concurrent review of each case in group II was conducted every day while a retrospective review of charts was conducted for patients in group I to determine patient care issues and identify abnormal trauma center test results.results: The number of patients with laboratory tests decreased from 97% in group I to 27% in group II (P <0.0001). Positive chemistry profiles increased (55% versus 92%; P <0.0001) as did coagulation profiles (8% versus 33%; P <0.0001). There were no differences in the percentage of patients receiving intervention based on laboratory data (7% in group I versus 8% in group II). No adverse effect on patient care was identified as a result of absent laboratory information in group II. Mortality, length of stay, and intensive care unit days were statistically unchanged. There was an annualized savings of $1.5 million in billed trauma center laboratory charges in group II.conclusion: Selective laboratory evaluation of trauma patients can greatly reduce medical cost and does not adversely affect care.