This longitudinal study examines the effects of exposure to the terrorist attack of September 11th as well as exposure to other forms of community violence on change in the mental health and social attitudes of youths in New York City. Three quarters of the youths reported some form of direct exposure to the events of September 11th, and 80% reported a lot of exposure to at least 1 form of media coverage of September 11th; these rates were comparable with the citywide survey of public school students in New York City conducted by the New York City Department of Education. Results of a structural equation model that included controls for previous levels of mental health and social attitudes, as well as a range of demographic factors, indicated that direct exposure and family exposure to the event did not predict change in any mental health outcomes, but did predict change in levels of social mistrust; media exposure did predict posttraumatic stress disorder symptoms. In contrast, victimization by other forms of violence was strongly associated with change in or current levels of all of the examined mental health symptoms, whereas witnessing other forms of violence was associated with change in or levels of 3 of 4 mental health symptoms and with increased hostile attribution bias and levels of social mistrust. Implications of the results for applied developmental and public mental health strategies in response to traumatic events are discussed. (Contains 6 tables and 1 figure.)