The purpose of this study was to examine the effect of September 11, 2001 on anxiety-related visits to selected Emergency Departments (EDs). We performed a retrospective analysis of consecutive patients seen by emergency physicians in 15 New Jersey EDs located within a 50-mile radius of the World Trade Center from July 11 through December 11 in each of 6 years, 1996--2001. We chose by consensus all ICD-9 (International Classification of Diseases, 9th revision) codes related to anxiety. We used graphical methods, Box-Jenkins modeling, and time series regression to determine the effect of September 11 to 14 on daily rates of anxiety-related visits. We found that the daily rate of anxiety-related visits just after September 11th was 93% higher (p < 0.0001) than the average for the remaining 150 days for 2001. This represents, on average, one additional daily visit for anxiety at each ED. We concluded that there was an increase in anxiety-related ED visits after September 11, 2001.