The psychosocial sequelae can be intense and of long duration in the aftermath of natural and technological disasters, as well as terrorist attacks. Posttraumatic stress symptoms and full syndrome disorder, depression, anxiety, somatic complaints, and excessive alcohol use have been demonstrated consistently, particularly following large-scale disasters. This paper examines the psychological research conducted at various intervals after extensive natural disasters, the Three Mile Island and Chernobyl technological accidents, and recent terrorist events in the United States. Factors predictive of the emergence of emotional distress and psychological and physical problems following a disaster also are discussed.