Estimates of acute mental health symptoms in the general population after disasters are scarce. We assessed the prevalence and correlates of acute posttraumatic stress disorder (PTSD) in residents of Manhattan 5-8 weeks after the terrorist attacks of September 11, 2001. We used random-digit dialing to contact a representative sample of adults living in Manhattan below 110th Street. Participants were interviewed about prior life events, personal characteristics, exposure to the events of September 11th, and psychological symptoms after the attack. Among 988 eligible adults, 19.3% reported symptoms consistent with PTSD at some point in their life, and 8.8% reported symptoms consistent with a diagnosis of current (within the past 30 days) PTSD. Overall, 57.8% of respondents reported at least one PTSD symptom in the past month. The most common past-month symptoms were intrusive memories (27.4%) and insomnia (24.5%). Predictors of current PTSD in a multivariable model were residence below Canal Street, low social support, life stressors 12 months prior to September 11th, perievent panic attack, losing possessions in the attacks, and involvement in the rescue efforts. These findings can help guide resource planning for future disasters in densely populated urban areas.