Tobacco smoking has been found to increase after the experience of a traumatic event and has been associated with posttraumatic stress disorder (PTSD). Initiation and persistence of cigarette smoking is moderately heritable; two recent investigations have implicated the COMT Val158Met (also known as rs4680) polymorphism in smoking age of initiation, dependence, as well as in quantity and frequency of smoking. To examine a possible association of COMT Val158Met and posttrauma increases in cigarette smoking, we studied 614 adults from the 2004 Florida Hurricane Study who returned saliva DNA samples via mail. PTSD was strongly associated with increased smoking. Moreover, each COMT Val158Met 'Met' allele predicted a 2.10-fold risk of smoking post-hurricane, independent of PTSD; follow-up analyses revealed that this finding was primarily driven by European-American males. This study represents the first genetic association study (to our knowledge) of smoking behavior following an acute stressor.