In this paper, an attempt has been made to provide guidelines for comparison of field, clinical and laboratory data on head injury. Difficulty in comparison arises due to the differing nature of the information that is produced in each type of investigation. Unconsciousness, dizziness, and loss of memory play an important role in determining the AIS code for an actual accident victim, but it is difficult to determine this kind of information from experiments on non-human primates. In the case of cadaver experiments, such information is not available at all. Details of internal brain injuries are not available for accident victims except those injured fatally and autopsied. On the other hand, in laboratory experiments on animals and cadavers, information on internal injuries can be obtained. These differences are discussed further and a guideline is proposed for interpreting injury data from different sources. An alphabetical list of head injuries is included along with AIS ratings for each injury. A methodology is proposed for evaluating multiple head injuries.