Individuals and communities are exposed to traumatic events, those that are accidents or naturally occurring and those that are intentional or human made. Although resilience is the expected response, for some, posttraumatic stress disorder may be the outcome. Brain models of PTSD require understanding the phenomenology of the disorder and the brain "break down" that occurs. Among several models, importantly, is the perspective that PTSD is a "forgetting" disorder. Other elements in the onset and triggers of PTSD can identify further models to examine at the bench. New studies of the 5-HT(2A) receptor, the glucocorticoid receptor, p11, mitochondrial genes and cannabinoids are bringing new perspectives to understanding brain function in PTSD. Effective treatments indicate areas for bench research on the mechanisms of the disorder.