To study child motion during vehicle deceleration, 167 simulations were conducted using a large three-dimensional gross body motion model program in which seven initial body positions, 2.5-, 3- and 6-year-old body sizes, three levels of panic braking deceleration, cases of superimposed crash decelerations and several seat sliding friction coefficients were considered. Predicted head impact times and velocities of impact are given and three-dimensional motion graphics presented for a number of the simulations which illustrate body and vehicle interaction and gross three-dimensional body motion. Also included are comprehensive data sets for body dimensions, inertial properties and initial three-dimensional position descriptions.