Objective: To estimate the risk of serious nonfatal injuries in frontal crashes among belted children seated in the right front seat of vehicles in which second-generation passenger air bags deployed compared with that of belted children seated in the right front seat of vehicles in which first-generation passenger air bags deployed. Design and Setting: We enrolled a probability sample of 1781 seat belt-restrained occupants aged 3 through 15 years seated in the right front seat, exposed to deployed passenger air bags in frontal crashes involving insured vehicles in 3 large US regions, between December 1, 1998, and November 30, 2002. A telephone interview was conducted with the driver of the vehicle using a previously validated instrument. The study sample was weighted according to each subject's probability of selection, with analyses conducted on the weighted sample. Main Outcome Measure: Risk of serious injury (Abbreviated Injury Scale score of >=2 injuries and facial lacerations). Results: The risk of serious injury for restrained children in the right front seat exposed to deployed second-generation passenger air bags was 9.9%, compared with 14.9% for similar children exposed to deployed first-generation passenger air bags (adjusted odds ratio, 0.59; 95% confidence interval, 0.36-0.97). Conclusion: This study provides evidence based on field data that the risk of injury to children exposed to deploying second-generation passenger air bags is reduced compared with earlier designs. Copyright 2005 by the American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use. American Medical Association, 515 N. State St, Chicago, IL 60610.