Injuries to the thorax in frontal impact accidents remain an important problem even for restrained occupants. During a frontal accident a significant portion of the forces restraining the occupant pass through the thoracic belt and deform the chest with the possibility of serious thoracic injuries. It is therefore important to understand the deformation of the human thorax when loaded by a thoracic belt and to understand how accurately crash dummies used in standard tests reproduce these deformations. This paper describes results of 19 tests in which a diagonal shoulder belt dynamically loaded the thorax of unembalmed cadavers and dummies (1). In all the tests, thoracic external deformations were measured using string potentiometers and two External Peripheral Instrument for Deformation Measurement (EPIDM) transducers (2).