This study was undertaken to determine factors that influence the access to trauma center care of pediatric and geriatric patients injured in motor vehicle collisions (MVC). Hospital discharge records for 1997 were obtained from the Pennsylvania Health Care Cost Containment Council and were analyzed. Of cases with an Injury Severity Score of > 15, 52.6% of elderly cases and 48.6% of pediatric cases were transported to and received their care in non-trauma center hospitals. These very high "mis-triage" rates could not be explained by differences in injury severity, body region or population density. In order to assess potential out-of-hospital factors, a file containing matched records from Emergency Medical Services (EMS) calls and hospital discharges from MVC cases across Pennsylvania for the year 1996 was constructed and analyzed. There were no significant vital signs differences between trauma center and non-trauma center cases, with the single exception of the Glasgow Coma Scale score, for both the pediatric and geriatric age groups. A reevaluation of out-of-hospital trauma triage is needed.