The aim of this study is systematically to evaluate and quantify the influence of interaction of car passengers in impacts.Within this programme 70 car tests were performed. The impact speeds were 30 and 60 km/h for the frontal and rear and 30 and 45 km/h for the lateral impacts. Impact angles were as follows: frontal: 0° and 30° left; lateral: 60° and 120° left, 90° right; rear: 180° and 150° left. Test cars were of subcompact type bought on the car market. Impacting vehicle was a rigid moving barrier according to SAE J 972a. Each of the 14 configurations was repeated 5 times. The effects of interaction were studied on 50 percent male PART 572 dummies.The significant effect of interaction is the change of direction of acceleration in the additionally loaded occupant, because the interaction forces are effective in the opposite direction of the primary impact forces. If interaction happens after the primary impact pulse is finished, high peak-to-peak acceleration levels with a considerable extension of acceleration pulse duration are the consequence. At the higher impact velocities, protection criteria of both dummies were very often exceeded. In oblique impact directions, occupant kinematics and interaction effects were much more complicated.