The horrific terrorist attacks on the United States on September 11, 2001, left an indelible mark on perceptions of security and threat across the world. This paper uses Schwartz's (1992) value circumplex model to examine value change across matched high school and university student samples in Finland, questioned before and after the World Trade Center (WTC) and associated attacks. In Study 1 (N 5 419), security values of adolescents were higher the day following the WTC attacks than before, but fell back toward pre-attack levels in the subsequent two samples. In contrast, levels of stimulation were lower following the terrorist incidents. In Study 2 (N 5 222), security levels of students were also higher following the WTC attacks, but again were closer to pre-attack levels in a subsequent cohort.The study of values has reemerged as a major topic for social psychological investigation in the past decade, with value systems seen as an important superordinate cognitive structure with considerable implications for individual behavior (Rohan, 2000;Schwartz & Bilsky, 1990). A variety of ecological life circumstancesFincluding political structure, historical experiences, and even climatic conditionsFhas been seen as central to the formation of value priorities (Hofstede, 2001;Schwartz, Bardi, & Bianchi, 2000), with adaptation and change in value priorities taking place through both the reinforcement contingencies offered by life circumstances and the individual's desire to fulfill outstanding deficit needs (Maslow, 1970;Schwartz & Bardi, 1997 Value change is usually seen as taking place over a relatively long time period, typically decades (De Vos, 1997;Hofstede, 2001), with value stability reinforced by occupational class structures that maintain value consistency across generations (Kohn, Naoi, Schoenbach, Schooler, & Slomczynski, 1990;Morgan, Alwin, & Griffin, 1979). Indeed, even when social and political structures undergo radical restructuring, as has been the case over the last decade in Central and Eastern Europe, there has been little evidence of significant value change (Schwartz et al., 2000).However, what happens to values in the short term, following a major traumatic and public event? The systematic study of the consequences of collective trauma following political violence is a relatively new topic of study (Ladd & Cairns, 1996;Raviv, Sadeh, Raviv, Silberstein, & Diver, 2000). Traumatic life events can challenge an individual's assumptive world, undermining implicit but fundamental beliefs and values (Janoff-Bulman, 1989). Clinical studies following terrorist incidents suggest a greater concern for family and personal safety following the witnessing of a terrorist incident (e.g., Applewhite & Dickins, 1997).Raviv and colleagues (Raviv, Raviv, Sadeh, & Silberstein, 1998;Raviv et al., 2000) studied school students' reactions to the assassination of Prime Minister Yitzhak Rabin, both immediately after the murder and 5 months later, as well as responses to a series of terrorist attacks in Israel. Their find...