Research has been undertaken into the injuries received by occupants of heavy goods vehicles (HGV's). Nationally in 1975 HGV occupant casualties represented only 2 percent of all vehicle occupant casualties. Of these only a quarter (800 casualties) sustained fatal or serious injury. Thus the numbers of casualties in HGV are relatively small, but when they do occur they are usually the result of impact between two HGV's or between an HGV and a roadside obstacle. The paper describes the findings of an in-depth investigation into the patterns and couses of injury in a sample of 59 seriously or fatally injured occupants of heavy goods vehicles. All fatal injuries were associated either with massive intrusion of the cab structure or with ejection of the occupants. This pattern of death is different from that found amongs unbelted passenger car occupants. A comparison is made between the patterns, causes and mechanisms of injury, more severe than minor, sustained by HGV occupants and by car occupants. Differences were found in the injury patterns and for causesof injury, particularly in respect of injury to the head, pelvis and lower leg. The data suggest that the wearing of seat belts by the occupants of HGVs might have reduced the severity of injury for about one third to one-half of the casualties in this small sample