In this paper human volunteer head/neck dynamic response is compared with that of a Hybrid III head and neck. The data base used for the comparison was taken from the extensive Naval Biodynamics Laboratory data base of human and manikin sled runs for various thrust vector directions. Significant differences were identified in the human volunteer and manikin responses for the −X and +Z runs, while an unexpected similarity was observed in the head trajectories for the +Y and −X+Y runs. A detailed analysis of 15 g −X vector exposures is presented. Math model simulations using a linkage model to simulate the response of the beam-like Hybrid III neck to −X sled acceleration profiles are presented, as well as simulations of human runs using a similar linkage model. Improved simulations were obtained by making changes to the linkage model parameters which could presumably be implemented relatively easily on the physical Hybrid III neck. Preliminary findings for the −X simulations indicate that it is possible to obtain quite human-like simulations by relocating the model neck/torso joint appropriately.