Studies in animals showing hippocampal atrophy and associated memorydeficits in stress and aging have implications for stress and aging in humans. Clinical studies intraumatized human populations with posttraumatic stress disorder (PTSD) have replicatedstudies in animals, showing reduction in volume of the hippocampus measured with magneticresonance imaging and associated memory deficits. Trauma at different stages of development(early childhood abuse versus trauma in later life due to combat) may influence the nature ofmemory deficits and hippocampal atrophy. Studies in aging human subjects are consistent withanimal studies, although future research is needed in this area. The similarities betweenbiological findings related to cortisol and the hippocampus in stress and aging in both animal andhuman studies raises the question of whether PTSD can be seen as a form of accelerated aging.Evidence that stress affects the hippocampus and the capacity for learning has broad implicationsfor public health policy, underlying the need for additional resources in this important area and areexamination of our understanding of factors influencing academic achievement.