Death and injury due to terrorist bombings continue to exercise civilian and military surgeons alike. In this paper 828 servicemen killed and injured by explosions in Northern Ireland have been studied, using data stored in the Hostile Action Casualty System (HACS). Because of the nature of the conflict in Northern Ireland, the magnitude of each explosion and the distance of the victims from it are quite accurately known. The overpressure (blast loading) to which the victim was exposed can be estimated from the information on the HACS forms and standard tables, giving overpressures for a given change at a known distance. Using the HACS data, the numbers of injuries due to overpressure (primary blast injury), missiles energized by the blast (secondary injury), displacement of the victim by the blast wind (tertiary injury) and flash burn can be determined. Of the 828 servicemen involved in explosions, 216 were killed, most of them before any treatment could be instituted. Of the servicemen in the survey, 90 per cent were wearing body armour. Although body armour affords considerable protection from secondary missiles, it is unlikely to reduce the number of deaths due to primary blast injury.