Three classes of introductory psychology students at the University of Pennsylvania completed a survey including several measures of group identification on 20 March 2001, 15 September 2001, and 24 March 2003. Importance of country and university were rated higher four days after the 9/11 terrorist attacks than six months before or 18 months after. Scores on a 9-item scale of identification with country were higher immediately after 9/11 than at the other two assessments. Four theories (group dynamics, CORFing, TMT, SIT) are considered; none predicts the whole pattern of results observed. Discussion highlights group dynamics theory for understanding the increase in identification with country and introduces the possibility that the increase in identification with university might have been a response to experiencing 9/11 as loss of control. Discussion also highlights the value of assessing level of identification with multiple identity groups in order to see the complexity of identity dynamics.