In order to identify cognitive and behavioral responses to trauma, we have studied responses to mass casualty body handling following the Gander, Newfoundland, plane crash of 1985 and the 1989 USS Iowa disaster, and responses to a simulated chemical and biological warfare environment. Individual and group trauma behaviors show prominent: (a) thinking by similarity (identification, and looking for the familiar/ seeing the past in the present); (b) attribution of meaning (rituals, symbols, language, and rumors); and (c) contagion of behavior. These processes highlight the importance of the study of responses to different traumatic stressors in order to identify cognitive mechanisms and behaviors activated by trauma. Such phenomena may be important to our understanding of the effects of traumatic stress and their acute and long-term health outcomes.