Almost all individuals who experience a severe trauma will develop symptoms of posttraumatic stress disorder (PTSD) shortly after the traumatic event. Although the natural history of PTSD varies according to the type of trauma, most people do not develop enduring PTSD, and, in many of those who do, it resolves within 1 year without treatment. To the extent that is possible, maintenance of normal daily activities is believed to help patients cope more successfully in the aftermath of major trauma. In the case of a disaster such as the Asian tsunami, the whole community is involved, and it is impossible to continue with normal daily activities. To improve overall outcome after trauma, it would be optimal to identify individuals at increased risk for developing PTSD. This article describes screening and assessment tools for posttrauma mental health problems, particularly PTSD, and examines in more detail instruments that can be used in rapid field assessment of individuals who may be affected or who have already been identified and require monitoring. Self-rated instruments are most appropriate, but the choice of instrument will depend on the local situation and availability of appropriately validated questionnaires. The article also addresses important aspects of training nonmedical personnel in screening and assessment.