September 11 created a natural experiment that enables us to track the psychological effects of a large-scale terror event over time. The archival data came from 8,070 participants of 10 ABC and CBS News polls collected from September 2001 until September 2006. Six questions investigated emotional, behavioral, and cognitive responses to the events of September 11 over a five-year period. We found that heightened responses after September 11 dissipated and reached a plateau at various points in time over a five-year period. We also found that emotional, cognitive, and behavioral reactions were moderated by age, sex, political affiliation, and proximity to the attack. Both emotional and behavioral responses returned to a normal state after one year, whereas cognitively-based perceptions of risk were still diminishing as late as September 2006. These results provide insight into how individuals will perceive and respond to future similar attacks.