Triage of potentially injured patients to the appropriate trauma hospital was carried out using mechanism of injury as a triage criterion rather than physiologic changes (trauma score). Injury mechanism includes field evidence of high energy transfer, such as falls of more than 15 feet, automobile accidents with structural intrusion, extrication difficulties, passenger ejection, or death at the scene. Evaluation of triage decisions for a 3 month period in 631 patients showed an overtriage rate of 14 to 43 percent. Using the trauma score alone would have missed significant injuries in at least 8 to 36 percent of these patients using the injury severity score or clinical criteria. Methods of evaluation of overtriage and undertriage are presented, but accepted standards for these must be addressed in each trauma system. Injury mechanism as a primary trauma triage criterion is an acceptable means of identification of potential injury for transport to a trauma facility.