PTSD is a psychiatric disorder that requires a traumatic event as diagnostic criteria. Brazil has high rates of violence, and it is expected that urban victims of violence would be at risk to the development of PTSD. Studies have associated the COMT val158met polymorphism with diminished stress resilience, reduced ability to extinguish conditioned fear, and the development of PTSD after multiple traumatic experiences. The aim of this study was to identify, in a case-control study, whether the val158met polymorphism (rs4860) is associated with the development of PTSD in a group of victims of urban violence. To our knowledge, this is the first study that examines the association between PTSD and urban violence. The polymorphism of COMT in PTSD patients (n=65) as well as in victims of violence without PTSD (n=34) and in a community control group (n=335) were genotyped. We found a significant relationship between the met allele (p<0.02) and PTSD among cases (PTSD+)and victims of violence without PTSD (PTSD-; OR 2.57) and between cases and community control group (p<0.003) Further analysis with larger samples and another ethnic group should be necessary to confirm our findings.