Computer simulations of occupant dynamics in frontal crashes have pretty much been done like sled tests, in that crash-induced deformation of the interior — which may be significant for the occupant — has usually not been accounted for. The object of occupant dynamics simulation studies is often to assess the effect of changes in vehicle front-end parameters on occupant response. But these parameter variations may influence the amount of interior deformation. In order to simulate more accurately occupant dynamics in very severe crashes, the interior deformation caused by engine intrusion should concurrently be simulated. Crash test results over a range of speeds were used in a computer simulation study of occupant compartment intrusion in high speed barrier crash tests. It was found that intrusion has a significant effect on occupant response and where appropriate should be included in crash simulations. For the crash conditions simulated, intrusion increases the restrained occupant's head and chest accelerations while no clear trend emerged for the unrestrained occupant.