THE FREQUENCY AND SEVERITY OF LESIONS SUSTAINED BY THE OCCUPANTS OF CARS IMPACTED LATERALLY depend upon the main following factors: impact localization, intrusion into passengers' compartment, car speed variation, direction of occupant trajectory, objects contacted by the various body areas. 296 lateral impacts are being described hereunder by means of factors below.Consequences are drawn therefrom as to the coming improvement of occupant protection taking account of the current state of the art in Biomechanics and automobile technique.IN COMPARISON WITH THE PROGRESS achieved with a view to improving occupant protection against frontal impact, the knowledge available on the lateral impact and the methods for reducing the severity thereof are very poor. In as much as the results achieved in biomechanics up to this date are known, there is still much to do in this field. Mc Elhaney (1)* already stressed the fact in 1971 after Snyder (2).Since that time, Stalnacker (1973) (3) proposed some tolerance thresholds for very localized impacts. Uncertainty still prevails.The analysis of real accidents must contribute to a better definition of the work to be accomplished in order to cut down risks.It is advisable to characterize the procedures for the most representative experimental impacts. It is also necessary to indicate which body areas are most often and most severely injured and to be more precise on the nature of injuries, whose severity should be reduced. Moreover, accidentology must permit to anticipate the number of fatalities which will be or might have been avoided by adopting any particular protection measure at a known performance level. The following study has for its purpose to supply some information on these points.