Fear is a critical emotional response that allows an organism to safely navigate through dangerous environments. The neural systems underlying the fear response have been well characterized, and include the amygdala, hippocampus, prefrontal cortex, bed nucleus of stria terminalis, nucleus accumbens, and others. While normally these brain regions coordinate to produce an appropriate fear response, the fear network in humans can become dysregulated after a traumatic event. The resulting phenotype of hyperarousal, avoidance, and re-experiencing of fear known as post-traumatic stress disorder (PTSD) is a growing problem in the United States. This chapter focuses on the role of the basolateral complex (BLC) of the amygdala, which has been implicated in the neuropathology of PTSD, particularly the hyperarousal, fear generalization, and fear extinction deficits characteristic of the disorder, as well as aspects of the microcircuitry, network connectivity, and neuromodulation of the BLC that may be involved in the pathophysiology of PTSD.