<div class="htmlview paragraph">An impact model of the human head characterized by an elastic spherical shell (skull) containing a low modulus core (brain) is studied using experimentally determined geometric, material, and structural properties. Injury criteria represented by skull fracture, brain cavitation, and brain shear deformation are interpreted and investigated in terms of effective acceleration-time thresholds. Contact stresses and durations are identified for head impacts typical in automobile collisions. In addition, selected comparisons of results with experimental data and head severity indices are given.</div>