This chapter examines current findings relating to the molecular neuropharmacology of posttraumatic stress disorder (PTSD). Studies consistently show that neurochemical alterations after trauma exposure are associated with the development of PTSD and reflect in part stress sensitization in PTSD. We also review neuroendocrine, neurotransmitter, neuropeptide, and related molecular features that reflect preexisting vulnerability factors for the development of PTSD. In this chapter, we provide an overview of recent neuroendocrine findings mainly with regard to the influence of the hypothalamic-pituitary-axis. We also review recent neurochemical findings including the influence of different neurotransmitters such as catecholamines, serotonin, amino acids, neuropeptides, neurotrophins, and lipids. We incorporate these new and established neurobiological findings into a proposed integrative model of the neurobiology of PTSD.