A longitudinal investigation of psychological responses to the September 11, 2001 terrorist attacks was conducted on a U.S. national probability sample. Using an anonymous Web-based survey methodology, data were collected among over 1, 900 adults at 2 weeks and 12 months post-9/11 to consider whether direct and proximal exposure were necessary preconditions for high levels of acute and posttraumatic stress symptoms, and whether greater exposure/proximity led to greater traumatic stress symptoms. Results suggest that the requirement of direct and proximal exposure to the attacks and the expectation of a dose-response relationship between exposure and traumatic stress response are myths. © 2005 by The Haworth Press, Inc. All rights reserved.