Secondary traumatic stress (STS) is used to describe the phenomenon whereby individuals become traumatized not by directly experiencing a traumatic event but by hearing about a traumatic event experienced by someone else. Such indirect exposure to trauma may occur in the context of a familial, social, or professional relationship. The negative effects of secondary exposure to traumatic events are the same as those of primary exposure including intrusive imagery, avoidance of reminders and cues, hyper-arousal, distressing emotions, and functional impairment. In the most severe instances, where symptoms result in significant distress or impairment in functioning, STS may warrant a diagnosis of posttraumatic stress disorder (PTSD). This entry defines terms associated with secondary traumatic stress, and then discusses the prevalence of STS and risk and resilience ...