We analyzed the 1988 through 1992 NASS field accident data on rollovers and injuries to occupants in these crashes. The data show that more than 96 percent of all occupants in rollovers do ggg receive serious head or neck injuries. The authors discuss why most restrained occupants do not suffer serious head or neck injuries in rollovers and how that helps us understand the injuries that do occur. Based on these data, the authors further developed the rollover injury parameter “residual headroom” to identify the likelihood of severe head/face or neck injury and the vehicle design measures that can mitigate those injuries. A theory of rollover head and neck injury causation is proposed that is supported by all available evidence and observations. ln particular, we will discuss how minor modifications of the roof structure and occupant protection systems of most contemporary passenger cars, light trucks, and vans can prevent severe injuries in rollovers.