This chapter presents the theory and development of psychological debriefing, looks at its outcomes, and discusses the difference between theory and practice. It also presents an alternative suggestion for the prevention of combat-related post-traumatic stress disorder (PTSD). Psychological debriefing has its roots in various forms of instrumental debriefing designed for the purpose of gathering information about, and drawing lessons from, a variety of tasks. Marshall's historical group debriefing is an important precursor of current psychological debriefing. The importance of debriefers being capable of identifying participants who are at risk for psychological morbidity has been stressed. Most of the evidence for the effectiveness of front-line treatment is based on clinical impressions in various wars. The findings showed that the more front-line treatment principles that a soldier's treatment incorporated, the more likely he was to return to his unit and the less likely to develop PTSD a year later.