While traffic accident fatalities in Japan have been declining, the number of injuries has continued on an upward trend for many years. One salient aspect of that rising trend is the number of casualties attributed to rear-end collisions. In 2005, such accidents accounted for approximately 35% of all fatalities and injuries. Regarding ordinary passenger cars, many of the drivers of the struck vehicles in rear-end collisions suffer slight neck injuries, while nearly all of the drivers of the striking vehicles are not injured. In this study, the influence of vehicle properties and human attributes on the incidence of neck injuries in rear-end collisions was analyzed using an integrated accident database developed by the Institute for Traffic Accident Research and Data Analysis (ITARDA). The results revealed, among other things, that an active head restraint system, which is one type of anti-whiplash device, is effective in suppressing the occurrence of neck injuries; that females tend to be injured more often than males; that age and generation influence the tendency for men to be injured; and that the trip purpose influences the tendency for neck injuries to occur. This tendency for generation and trip purpose to exert such an influence suggests the possibility that the health consciousness of the parties involved in rear-end collisions might affect the incidence of neck injuries. Among the other issues discussed in this paper is the concern that neck injuries due to rear-end collisions might increase in the future.