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Objective: There have been deaths and casualties in an explosion which happened in an industrial region in Ankara in February 2011. The aim of this study is to determine the prevalence of acute stress disorder (ASD), and post-traumatic stress disorder (PTSD), to assess the cognitive beliefs about their personalities and to determine the sociodemographic variables and cognitive beliefs which can be the risk factors for PTSD. Methods: One hundred and ninety-seven individuals, who were present at the factory building where the explosion happened and at the four offices nearby, were included in the study. Sociodemographic information form, Personality and Belief Questionnaire-Short Version, clinician administered Post-Traumatic Stress Disorder Scale were applied to the participants one month after the explosion. The psychiatric assessments were done using the structured clinical interview for DSM-IV axis-1 disorders (SCID-I). Results: The prevalence of ASD and PTSD were 37.1% and 13.7% respectively. Having major depressive disorder before the incident, physical injury, acquaintances among the dead and the injured, being in the centre of the incident and seeing dead bodies were detected as risk factors for PTSD. Obsessive-compulsive personality beliefs in PTSD and avoidant personality beliefs in ASD were found higher statistically. Conclusion: ASD and PTSD was detected common after the explosion. Generalized anxiety disorder in the past for ASD, and major depression for PTSD were detected in the individuals. It was also determined that avoidant and obsessive personality traits were seen more common in the individuals who had symptoms related to post traumatic stress. It is important to detect the other psychopathologies, specific beliefs about personality and possible risk factors in the individuals who have PTSD and ASD for mental health protection. (Anatolian Journal of Psychiatry 2012; 13:270-276) Key words: [Anadolu Psikiyatri Derg 2012; 13(4.000): 270-276]