Only recently, Brazilian psychiatry has acknowledged the importance of the diagnosis of posttraumatic stress disorder (PTSD). Despite the fact that Brazilians have a high prevalence of exposure to traumatic events, such as accidents and homicides, there are few theoretical and empirical studies about PTSD in Brazil. This paper provides a brief review of the diagnosis of PTSD. Following a discussion of the main issues on the definition of traumatic event, we focused our discussion on the challenges of the psychiatric examination of patients with PTSD. In the last section of the paper, the authors emphasize the description of the PTSD symptoms and provide clinical vignettes to illustrate important psychopathological concepts. In conclusion, the importance of the diagnosis of PTSD in psychiatry is highlighted inasmuch as it provides an observational framework for investigating the effects of stress and trauma.