The objective of this presentation is to discuss certain biomechanical aspects of head injuries due to blunt and penetrating impacts. Emphasis is given to fundamental data leading to injury criteria used in the United States (US) regulations for motor vehicle safety. Full-scale and component tests done under US Federal Motor Vehicle Safety Standards (FMVSS) are described. In addition, results providing occupant safety and vehicle crashworthiness information to the consumer from frontal and lateral impact crash tests are discussed with an emphasis on head injury assessment and mitigation. In the area of penetrating impact, newer experimental techniques are described for a better understanding of head injury secondary to penetrating impacts, with specific reference to the civilian population.