The air bag system is described in terms of four basic elements: the crash sensors and controls, the inflator, the air bag itself, and the diagnostic circuitry. A general discussion of these elements is provided and a review of air bag related injuries is also presented which includes data from various sources such as the University of Michigan Transportation Research Institute, National Highway Traffic and Safety Administration, Transport Canada, and the Insurance Institute for Highway Safety. The most frequently occurring accident type is the frontal collision and has been the main focus of safety efforts with regard to restraint systems. Air bags are an effective injur/prevention device, however their deployment can introduce new injury mechanisms. Air bags save lives and decrease the severity of major injuries in exchange for increasing the number of minor injuries. Certain risk factors exist during an accident involving air bag deployment including occupants sitting in close proximity to the air bag module (often small women) and unbelted occupants who move forward early in a crash or during precrash braking. The body regions most frequently injured are the head and neck, followed by the upper extremities, and then the lower extremities. Abrasions, contusions, and lacerations are identified as the injuries most often observed. Among the most severe air bag induced injuries are those to the eye, but these occur infrequently. From the review of injuries related to air bags, it appears that deployment of untethered air bags, closeness to air-bag module or proximity to the steering wheel, and high velocity of deployment (high capacity inflator) are potential causal mechanisms.