Stress affects all participants at a crisis incident: responding officers, crisis response team, hostage takers, hostages. The ability of negotiators to effectively recognize stress and help manage the stress among participants can mean the difference between success and failure. This chapter deals with stress and how to manage stress, including post-traumatic stress. Stress and how it affects a person are defined and described. The effects of stress on each participant are described separately, as the stressors on each participant are unique to their role in the incident. For example, stress experience by negotiators is due to different factors than stress experienced by the hostage taker. Emphasis is given to techniques and strategies that can be used to manage stress among participants. Upon an incident’s resolution, negotiators and other law enforcement participants should conduct operational debriefings and, depending upon what happens during the incident, an emotional debriefing. Guidelines for conducting these debriefings are presented and critical issues to address in each given. Trauma and stages of trauma are presented. Post-traumatic stress disorder is explained, along with how it affects people. Recent research dealing with PTSD is presented. Guidelines that can assist negotiators in dealing with PTSD (and others in the incidents) are described. For hostage takers who may be experiencing PTSD, risk assessment guidelines are discussed.