Head injury is the most common cause of death and acquired disability in childhood. We seek to determine the influence of brain mechanical properties on inertial pediatric brain injury. Large deformation material properties of porcine pediatric and adult brain tissue were measured and represented by a first-order Ogden hyperelastic viscoelastic constitutive model. A 3-D finite element mesh was created of a mid-coronal slice of the brain and skull of a human adult and child (2 weeks old). Three finite element models were constructed: (1) a pediatric mesh with pediatric brain properties, (2) a pediatric mesh with adult tissue properties, and (3) an adult mesh with adult tissue properties. The skull was modeled as a rigid solid and an angular acceleration was applied in the coronal plane with center at C4/C5. The brain is assumed to be homogeneous and isotropic. A fourth simulation was analyzed using the adult mesh and adult material properties with a reduced load as proposed by Ommaya (Ommaya et al, 1967). Peak maximum principal logarithmic strains (LEP3) were determined in each of the simulations. Overall, brain size and material properties both affected the intracranial tissue deformation field, with brain size having the greater influence. On average, strains in pediatric and adult models produced by loads scaled using Ommaya''s relationship (1967) were similar, when material properties were assumed to remain constant. When experimentally obtained material properties of adult and pediatric brain tissue were used in the simulations, the scaled loads produced larger strains in the adult model than the pediatric model.