The introduction of airbags has not significantly reduced serious thoracic injury for belted occupants in frontal crashes. This thesis has investigated the effectiveness of airbags and the characteristics of residual thoracic organ injury incurred by belted occupants in vehicles equipped with airbags. This study was based on the injury outcome of over 28,000 belted front seat occupants involved in frontal collisions. Data for this analysis was extracted from National Automotive Sampling System / Crashworthiness Data System (NASS/CDS) case years 1993-2007. The use of odds ratios for comparing the effect of airbags on the occurrence of injury has shown that airbags do not significantly increase protection against head and chest injuries. Overall, the lower extremity and the upper extremity were shown to be adversely affected by airbags. The face was the only body region that was shown to benefit from the combination of seat belts and airbags as compared to seat belts alone. An investigation into the characteristics and distributions associated with thoracic organ injuries showed the heart and great vessels are the only thoracic organs that showed a significant reduction in the rate of injury with the inclusion of airbags. In vehicles with airbags, the thoracic organs are injured more frequently than the ribs. When occupants sustain thoracic organ injury, the delta-V of the crash for vehicles with and without airbags is not significantly different. The odds of serious injury to the lungs and spleen are higher for occupants in vehicles with airbags as compared to those in vehicles without airbags. Rib fracture was found to be a poor predictor of moderate to fatal thoracic organ injury. Only 31-61% of thoracic organ injuries occur with an associated rib fracture.