Manhattan residents living near the World Trade Center may have been particularly vulnerable to posttraumatic stress disorder (PTSD) after the September 11, 2001 (9/11) terrorist attacks. In 2003-2004, the authors administered the PTSD Checklist to 11,037 adults who lived south of Canal Street in New York City on 9/11. The prevalence of probable PTSD was 12.6% and associated with older age, female gender, Hispanic ethnicity, low education and income, and divorce. Injury, witnessing horror, and dust cloud exposure on 9/11 increased risk for chronic PTSD. Postdisaster risk factors included evacuation and rescue and recovery work. The results indicate that PTSD is a continued health problem in the local community. The relationship between socioeconomic status and PTSD suggests services must target marginalized populations. Followup is necessary on the course and long-term consequences of PTSD.