Head and neck injuries are a substantial source of morbidity and mortality in children in the US, accounting for about 30% of child deaths and $10 billion in estimated annual cost (CDC 1990;​ Kraus et al. 1990;​ James et al., 1999). To study these injuries, providing routes for potential injury prevention, computational Finite Element Models (FEM) of children must have representative constituent material properties. This study focuses on the strain softening properties of the dura mater, the phenomenon whereby a material experiences a decrease in stiffness after undergoing previous strain. This behavior may be important in computing dynamic response in impact and failure scenarios (Kirton et al;​ 2005), especially in young children, and is rarely characterized. Eleven post-mortem human subjects (3-adult;​ 9-pediatric) were used to produce 46 dura mater samples. Each sample was repeatedly loaded to three increasing strain levels, including 1/24, 1/12, 1/8, 1/6, 1/3 and 1⁄2 of the estimated average yield strain of the dura mater. Changes in modulus, peak stress and hysteresis energy were analyzed. Strain softening was characterized using a strain amplification factor, the change in the Young’s modulus of the dura as it undergoes repeated loading at increasing strain levels. In oscillatory tests to 2% Lagrangian strain, there was a 9.7% decrease in peak stress and a 39% decrease in hysteresis energy loss from the first to the last cycle. In contrast, for strains larger than 2%, there was a 28% decrease in peak stress and a 68.9% decrease in hysteresis energy loss from the first to the last cycle. These differences suggest evidence of strain softening at large strain levels.