Triage decisions must be based on accurate information with a valid understanding of injury patterns and their sources. Only a data base that includes both medical and collision factors can best provide the breadth of information required to achieve this goal. In this study we assessed the accuracy of automobile collision data collected by emergency physicians when compared to Police Accident Reports. The emergency medicine attending physicians obtained data concerning vehicle collision factors for all automobile collisions during a two month period resulting in major trauma patients over 18 years of age that were triaged to the Emergency Department at Stanford University Hospital, a Level I trauma center. These data were then compared by one of the investigators against Police Accident Reports, which were available for 50 of the 64 patients that met the study eligibility criteria. Nearly three-fourths (74%) of all cases had at least one discrepancy when compared with the Police Accident Reports, while 46% of these had multiple discrepancies.