One of the main changes in DSM-5 is associated with for post-traumatic stress disorder (PTSD). Previously (DSM-IV), PTSD were classified under the anxiety disorders group. In DSM-5, It is classified under the main heading of “trauma and stressor-related disorders” with psychiatric disorders with common etiological factors. Diagnostic criteria of PTSD are now grouped under five main titles with DSM-5. These main titles are summarized as; having a serious trauma (A), re-experiencing the trauma (B), avoidance symptoms (C), negative cognition, mood related symptoms (D), aggressiveness, and hyperarousal symptoms (E). Changes associated with the definition of traumatic event which causing psychiatric disorder are made. Definitions about subjective components of traumatic event in DSM-IV were removed, but instead it, definitions, which will help to identify the traumatic event were added. Brieşy, criterion A (the traumatic event) has been tried to purify from subjective components and traumatic events were described in an objective way. Definition has been expanded, since items related with the impact of event over the patient have been removed. Diagnostic criterion B is simplified with DSM-5. Borders of diagnostic criteria B were clarified with a definition of re-experiencing comprising dissociative features. According to new criteria, diagnostic criterion C was completely organized as an item related to avoidance. Mood-related items were removed. Some authors have interpreted this situation as clearing the borders between PTSD and other mental disorders and highlighting the mood features of PTSD. Criterion D consists new forms of mood symptoms and negative cognitions which took part in the old diagnostic criteria. According to some authors, mood symptoms in PTSD had the opportunity of expanded definition with these criteria. E criterion carries the nature of a novelty for PTSD. By this criterion, aggression and impulsivity of patients with PTSD which are frequently encountered, are set out in a clear format. PTSD identification in DSM-5 (especially criteria D and E) has been targeted to explain of many symptoms of patients without the need for some comorbid diagnosis. Unlike symptoms of anxiety in the DSM-IV, depressive symptoms were clearly defined. Remaining of anxiety symptoms so behind of depressive symptoms or the expression of depressive symptoms so clearly bring to mind the question that have DSM-5 tried to create compelling reasons to the fundamental change in the classification. Rigid and clear statements were used rather than more inclusive and expanded changes for the description of the traumatic event. Another significant change in DSM-5 is identification of dissociative subtype. It is considered the identification of this subtype based on the hypothesis that some people’s reactions to traumatic events are mainly in the form of dissociative reactions so that they reveal a coping strategy with intense anxiety and fear. In one aspect, this definition create open field to neurobiological studies and treatment-related researches, on the other hand it may cause legal problems. Even, there are comments that this situation might cause secondary gains. These new criteria will be tested more accurately by clinical practices and studies. PTSD prevalence is reported to be similar in terms of DSM-IV and DSM-5 diagnostic criteria