BACKGROUND: The availability of automotive airbags continues to increase in an effort to reduce traffic fatalities. Their benefits do not come without consequences, as front and side airbags have been linked to upper and lower extremity injuries. This study sought to test the hypothesis that occupants of vehicles equipped with side airbags, involved in side impact motor vehicle collisions, have an increased risk of upper extremity injury when compared with occupants of vehicles without side airbags. METHODS: The risk of upper extremity injury in side impact collisions was compared between vehicles with and without side airbags using data obtained from the 1995-2004 Crashworthiness Data System, a dataset maintained by the National Highway Traffic Safety Administration. We assessed the risk of upper extremity injury as classified by Abbreviated Injury Scale score, 1990 Revision. RESULTS: Although there was no association between side airbag availability and the risk of upper extremity injury overall [risk ratio (RR) 1.08; 95% confidence interval (CI) 0.85-1.36], the risk of a moderate or serious upper extremity injury (Abbreviated Injury Scale score ≥2 or ≥3 injury) was significantly increased (RR 2.75, 95% CI 1.10-6.83 and RR 2.45, 95% CI 1.00-5.96, respectively). The risk of dislocation was also increased (RR 2.42, 95% CI 1.26-4.64), although there was no difference in the risk of fracture (RR 1.00, 95% CI 0.53-1.89). CONCLUSION: The forces generated by airbag deployment may explain the increase in upper extremity injuries observed in vehicles equipped with side airbags. This increased risk must be balanced against other research suggesting reduced risks for head and thoracic injury. © 2008 Lippincott Williams & Wilkins, Inc.