This paper is the summary of the current state of the art in the multidisciplinary science of biomechanics as it relates to head injury. A review of typical occupant dynamics is presented, and injury causation mechanisms are examined. The history of methods used to measure impact severity and human tolerance levels to impact is reviewed and possible modifications of the Head Injury Criteria (HIC) are explored. Engineering analysis of individual cases is suggested to evaluate the response of the head and brain to impact. A bibliography of technical literature on head injury is included.