Early analyses following the September 11 terrorist attacks on New York City showed an increase in cigarette, alcohol, and marijuana use, but it was unknown whether these increases would persist. A random-digit dial phone survey was conducted to estimate the prevalence of increased substance use among residents of New York City six to nine months after the attacks. Among 1570 adults, 9.9% reported an increase in smoking, 17.5% an increase in alcohol use, and 2.7% an increase in marijuana use compared to the month before September 11. These increases were comparable to increases reported in the first one to two months after September 11. Persons who increased use of cigarettes were more likely than those who did not to report symptoms consistent with posttraumatic stress disorder (PTSD) in the past month (4.3% and 1.2% respectively). Depression was more common among those who increased use of cigarettes (14.6% and 5.2% respectively), alcohol (11.8% vs. 5.2%), and marijuana (34.1% vs. 5.3%). Among residents living in Manhattan below One Hundred Tenth Street, the prevalence of PTSD and depression declined by more than half in the first six months after September 11, while the increase in substance use did not decline substantially. These results suggest that the increase in substance use after a disaster may be a cause for public health concern in the long-term.