Comfort and safety are major considerations in the design of occupant seats in motor vehicles. In rear impacts, the seat is the principal component of the occupant restraint system. However, it also contributes to occupant restraint in frontal. and side impacts, and rollovers.To determine how well automobile seats protect occupants from injuries in rear impacts, crash data from the national accident files in the united states were analyzed. The distributions and causes of injuries in rear impacts were categorized according to injured body region and source of injury. In addition, forty-nine selected accident cases were reviewed, to determined how the seat performed in crashes. Finally, rear impact crash tests of passenger cars were analyzed to determine dummy motion and seat performance.Non-contact injuries were associated with the largest portion of injury harm. The seat and frontal components were the two largest sources of contact injury harm. For restrained occupants, the harm distribution was: Non-contact - 25%; Seat - 22%; Front - 16%. For the 49 cases reviewed, nearly half of the occupants in severe rear impacts received injuries from frontal components inside the car. Three occupants in severe crashes received AIS 2 neck fractures. All three were in seats with backs which did not deform during the crash.Opportunities for safety improvements include improved head restraints, seats designed to absorb energy, and belt/seat systems which act together to protect the occupant in both rear and frontal impacts.