The classification of liver injuries is important for clinical practice, clinical research and quality assurance activities. The Organ Injury Scaling (OIS) Committee of the American Association for the Surgery of Trauma proposed the OIS for liver trauma in 1989. The purpose ofthe present study was to apply this scale to a cohort ofliver trauma patients managed at a single Canadian trauma centre from January 1987 to June 1992.170 study patients were identified and reviewed. The mean age was 30, with 69% male and a mean ISS of 33.90% had a blunt mechanism ofinjury. The 170 patients were categorized into the 60IS grades ofliver injury. The number of units of blood transfused, the magnitude of the operative treatment required, the liver-related complications and the liver-related mortality correlated well with the OIS grade. The OIS grade was unable to predict the need for laparotomy or the length of stay in hospital. We conclude that the OIS is a useful, practical and important tool for the categorization of liver injuries, and it may prove to be the universally accepted classification scheme in liver trauma.