Forty-eight lateral impact accidents were studied correlating vehicle damage and occupant injury. Side-swipe accidents produced serious injury only when the occupant's elbow was protruding through a window or when the occupant space of the vehicle was seriously compromised. Intersection impacts and drifting impacts, particularly when the impact was caused by a vehicle approaching from the opposite direction, caused the most serious injuries. Fractures of the acetabulum with intrapelvic protrusion of the hip and fractures of the pubic rami are characteristic of lateral impact accidents. The door was the most common injury-producing structure of the vehicle. Deep wrap-around seat designs and stronger doors, door frames, and chassis structures are necessary to reduce occupant space penetration and to absorb impact energy in lateral impact accidents.