One of the most exciting developments to emerge from the field in the past 20 years is the increasing attention to neurobiological responses to violence and trauma exposure. Although researchers have yet to identify a consensual pattern of neurobiological response to violence and trauma exposure, it does appear that some type of alteration in the hypothalamic pituitary adrenal (HPA) axis is likely. This article briefly reviews the multiple moderating factors that help account for the divergent patterns in HPA function as well as methodological advances that will continue to improve the assessment of HPA function in youth exposed to violence and trauma.