Distribution of load has a major influence on type and severity of chest injuries. The introduction of the Hybrid III dummy into crash testing along with the requirement to measure sternum deflection for injury assessment has brought about the need to evaluate how well its thorax senses various loading conditions. Tests revealed that different load distributions, i.e. due to a diagonal shoulder belt or an airbag, did not produce the expected chest deflection patterns. This appears to be the result of both a relatively stiff sternum assembly and a nonsuitable design of the clavicle. Chest compression responses became more realistically when both, sternum and clavicle of the Hybrid II were mounted into the Hybrid Ill's thorax. As a consequence, this study suggests that the thorax of the Hybrid III dummy must be improved.