The extent to which individuals involved in road traffic accidents suffer long term disability has been inadequately researched. There is insufficent knowledge about the duration of any such disability, the effect on post-accident routine or the cost to the community. Furthermore little is known about the relationship, if any, between the duration or severity of disability and the severity or type of the initial injury. This report describes work which aimed to determine whether there is any correlation between injury severity and subsequent disability, whether such disability was a consequence of particular injuries and whether the effects of long term disability should be included when costing road accidents. It was concluded that up to 24 per cent of all patients who had been involved in a road traffic accident developed a disability which lasted at least six months. The commonly used Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS) were found to be of little value in predicting the development of a disability. Only 28 per cent of patients with a residual disability were admitted to hospital, so that the examination of in-patient data alone would be likely to underestimate significantly the number of disabilities resulting from road accidents. Those injuries associated with the highest incidence of long-term disability were soft tissue injuries to the cervical spine ('whiplash' injuries) and closed fractures of the lower limbs. Present methods of costing road accidents which take account principally of in-patient costs are likely to underestimate their true cost. Further work on injuries resulting in a high incidence of disability and into the cost of out-patient resources is suggested. (TRRL)