Two child restraint system sled tests with a child cadaver* and a 3-year old child dummy have been carried out at the Highway Safety Research Institute of The University of Michigan. Some differences between the kinematical response of dummy and cadaver were found. Two mathematical models have been formulated, using the MADYMO program package, for the special purpose of evaluating child restraint performance. A description of the validated dummy and cadaver model is presented together with a comparison of experimental and model results. A sensitivity study was conducted to have a better insight into the effects of various parameters on the child's response. To show the use of the model as a design tool, a simulation with an energy absorbing backstrap is presented. It is concluded that the mathematical model is a better simulation for the cadaver kinematics than the dummy.