The Abbreviated Injury Scale (AIS) is an anatomy-based coding system created to classify and describe the severity of injuries. It represents an assessment of the severity of injury including the threat to life associated with the injury.  AIS is one of the most common anatomic scales for traumatic injuries.  AIS consists of a single coding dictionary.  The first version of the scale was published in 1969 with major revisions or updates in 1976, 1980, 1985, 1990, 1998, 2005, 2008, and 2015.

The AIS codes three aspects of injury: type, location and severity.   The AIS severity has a scale of 1 to 6, one being a minor injury and six being maximal.  An AIS severity of 6 is not the arbitrary code for a deceased patient or fatal injury, but is used only for specific injuries assigned an AIS 6 severity.  An AIS severity of 9 is used to describe injuries for which not enough information is available for more detailed coding, e.g. crush injury to the head.

The AIS scale is a measurement tool for single injuries.  A well accepted injury aggregation function is the Injury Severity Score (ISS).  It has several derivatives that have unique applications.  In other settings such as system design and occupant protection, maximum AIS (MAIS) is a useful tool for the comparison of specific injuries and their relative severity, and the changes in those frequencies that may result from evolving system design.