The effect of side airbag in reducing chest injury in car-to-car side impacts was studied using a human FE model (THUMS). A simulation was conducted assuming that a car was struck by another car at 50 km/h impact speed. Injuries were predicted for both front and rear seat occupants, and compared between cases with and without side airbags. Rib fractures were observed in the inferior thorax regardless of seating position without side air bags. With side air bags, on the other hand, the number of rib fractures was reduced because of smaller local deformation. The study also compares responses between the THUMS and the Euro-SID2 dummy model.