What's the post-traumatic stress disorder? Post-traumatic stress disorder (PTSD) is a major public health problem by virtue of its frequency, chronicity and the disability it generates in daily life. PTSD has been known since Antiquity and explored by military psychiatrists and early psychoanalysts, but today more than ever it is a topical issue because of the large number of events such as terrorist attacks or meteorological disasters that occurred lately in France and outside the country. This disorder is characterized by four main dimensions: reexperiencing, avoidance, hyperarousal, and cognitive and mood disturbances. Sleep is very often disrupted and comorbidity is common. The suicidal risk is also frequent. PTSD can affect anybody even though a number of individual risk factors have been identified, such as gender, socio-economic status and psychiatric or traumatic history, with a special focus on peri-traumatic dissociation. As we know, this disorder is the result of exceptional events but is can also be the consequence of more "daily" events which general practitioners are often the first to be consulted for. Despite an apparent "popularization" of the symptoms by greater media coverage, this specific disorder is still poorly understood in its definition and in routine medical practice.