The introduction of airbags has not reduced serious thoracic injury for belted occupants in frontal crashes. Questions have been raised regarding the ability to advance this technology with respect to its effectiveness at protecting belted occupants. This thesis investigated the effectiveness of airbags and the characteristics of residual thoracic organ injury incurred by belted occupants in vehicles equipped with airbags. Belted front seat occupants in frontal collisions from NASS/CDS case years 1993-2007 were analyzed. 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 the most 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 than the ribs. Also, the average delta-V associated with serious thoracic organ injury was not different with and without an airbag available. 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 is a poor predictor of moderate to fatal thoracic organ injury. Only 31-61% of thoracic organ injuries occur with an associated rib fracture.