.A number of articles in professional journals and newspapers have questioned the effectiveness of supplemental air bags. The articles maintain that insurance injury claims have increased after adoption of air bag systems and thus air bags provide no net benefit. The insurance industry itself disagreed with this interpretation of its own data, but their protest is not highly publicized.The object of this paper is to shed light on the effectiveness of air bags using the National Accident Sampling System (NASS) of the National Highway Traffic Safety Administration (NHTSA). Our results indicated that the air bags are doing what they were designed to do, that is, to decrease the severity of injuries in major accidents. On the other hand, air bags sometimes might cause minor injuries, when no injury would have occurred without air bags. Since minor accidents are more frequent than major accidents, the frequency of injuries might increase when air bags are introduced. This does not mean that air bags are ineffective; on the contrary, the air bags decrease the severity of major injuries in exchange for increasing the number of minor injuries, surely a desirable design tradeoff.