The William Lehman Injury Research Center has conducted multi-disciplinary investigations of fifty crashes involving drivers protected by air bags. In all cases, serious injuries were suspected. Nine cases involved fatal injuries. These cases are not representative of crashes in general. However, when used in conjunction with NASS/CDS they provide insight into the most severe injuries in crashes of vehicles equipped with air bags.A comparison with data from the National Accident Sampling System; Crashworthiness Data System (NASS/CDS) shows that head injury and abdominal injury make up a larger fraction in the Lehman data than in NASS/CDS. Examination of fatal cases indicates that head injuries are frequently caused by intruding structure or by unfavorable occupant kinematics among the unrestrained population. The more precise injury examination provided to patients admitted to a Level I Trauma Center may contribute to the higher proportion of abdominal injuries observed at the Lehman Center.Serious upper extremity injuries are rare in the Lehman data, but contribute a large harm fraction in NASS/CDS. The upper extremity injuries in NASS/CDS occur predominately at the lower crash severities.Both NASS/CDS and Lehman data indicate that lower extremity injuries are an increasing harm factor among occupants in severe crashes.The Lehman data suggests that air bags are remarkably effective at high severity frontal crashes. However, in some rare events, the protection at low crash severity may be less than without the air bag.