Background Triage and interhospital transfer are central to trauma systems. Few studies have addressed transferred trauma patients. This study investigated transfers of variable distances to OUH (Oslo University Hospital, Ullevål), one of the largest trauma centres in Europe. Methods Patients included in the OUH trauma registry from 2001 to 2008 were included in the study. Demographic, injury, management and outcome data were abstracted. Patients were grouped according to transfer distance: ≤20 km, 21-100 km and > 100 km. Results Of the 7.353 included patients, 5.803 were admitted directly, and 1.550 were transferred. The number of transfers per year increased, and there was no reduction in injury severity during the study period. Seventy-six per cent of the transferred patients were severely injured. With greater transfer distances, injury severity increased, and there were larger proportions of traffic injuries, polytrauma and hypotensive patients. With shorter distances, patients were older, and head injuries and injuries after falls were more common. The shorter transfers less often activated the trauma team: ≤20 km -34%; 21-100 km -51%; > 100 km -61%, compared to 92% of all directly admitted patients. The mortality for all transferred patients was 11%, but was unequally distributed according to transfer distance. Conclusion This study shows heterogeneous characteristics and high injury severity among interhospital transfers. The rate of trauma team assessment was low and should be further examined. The mortality differences should be interpreted with caution as patients were in different phases of management. The descriptive characteristics outlined may be employed in the development of triage protocols and transfer guidelines.