Children's reactions after being exposed to mass violence may be influenced by a spectrum of factors. Relatively unexplored is the extent to which family exposure to mass violence may affect child mental health, even when these children have not been directly exposed. In a representative sample of NYC public school children assessed 6 months after the September 11, 2001 attack on the World Trade Center (WTC), seemingly elevated rates of psychopathology were recorded among children of WTC evacuees. Children of NYC First Responders (police officers, EMTs, and fire fighters) displayed a complex pattern of response to the WTC attack. Overall, the findings from this previous study support putative transmission of trauma to children whose parents were exposed to the WTC attack. The "Children of First Responder and WTC Evacuee Study"--a two-site longitudinal study--is currently underway in the United States (New York City) and in Israel (Tel Aviv area) in an effort to understand the impact of different patterns of mass violence. The NYC sample permits us to examine the impact of a rare instance of mass violence (e.g., WTC attack), while the Israeli sample provides information about repeated and frequent exposure to mass violence brought about by acts of terrorism. In addition, children's exposure to mass violence is considered in the context of their exposure to other potentially traumatic events. This study aims to improve our general understanding of the impact of mass violence on children, especially the psychological effects on children whose parents' work experiences are by nature stressful. Knowledge generated by this study has implications for guiding efforts to meet the needs of children who have, directly or through a family member, been subjected to rare or infrequent mass violent event as well as to children whose exposure to mass violence is part of daily life.