During the last three years, our Group which is entitled FOC - bringing together the Faculté de Médecine in Marseille. The Organisme National de Sécurité Routiére, and the Citroën-PSA Group, has been investigating experimental lesions produced by impacts of vehicles against pestrians.The Authors of this study are all researchers in this field, and face the problem of evaluating quantitatively the severity of the different lesions that are observed, whether these be isolated or associated with others. Application of the AIS scaling method is a procedure which has the merit of existing, of being understood and of being adopted throughout the world ; from our own direct experience it has however seemed to us necessary to draw attention to the imperfections of this method, doing so on the basis of fifty homogeneous impacts that have been studied. From the moment when the morphological analysis of cadaver investigations is performed, obvious distortions are observed. These distortions will be confirmed later on, by examination of the clinical files.Since our purpose in analysing the lesions produced by different types of vehicule was to be able to make proposals to vehicle manufacturers concerning the shapes and structures of bodywork that would be less injurious, it has seemed essential to us that the AIS scaling method should be complemented by a certain number of additional parameters.