A recent campaign by the National Institute for Prevention and Health Education (INPES) has raised public awareness about depressive disorders. The prevalence data used are based on epidemiological surveys of the general population that employ instruments whose design methods must be understood in order to properly identify the scope of their interpretation. This article explains what is meant by "depression" in an epidemiological survey and presents the prevalence rates of such disorders obtained from the 2005 Inpes Health Barometer. The focus here is on Major Depressive Episode (MDE), whose diagnostic criteria are defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR). The 12-month prevalence of this disorder is assessed using a tool applicable to the general population, the CIDI-Short-Form. The prevalence of subsyndromic depressive symptoms is 19%; 7.8% of individuals experienced a MDEP, of whom 4.2% had a moderate-intensity MDEP and 3.2% a severe MDEP. Forty-eight percent of those who experienced such an episode in the past 12 months had at least two. Fifteen percent have a chronic disorder. In light of these results and the particularly harmful consequences of major depressive disorders, especially severe ones, these analyses confirm the public health issue they represent and the value of a national information campaign. (R.A.).