Selective mutism was first described in the medical literature 140 years ago. The diagnosis came into the focus of adult psychiatry with the appearance of DSM-5. Henceforth, selective mutism during infancy, adolescence and also adulthood is specified as an independent anxiety disorder. It often begins in early childhood with a kind of speechlessness in certain situations. A diagnostic clarification often only takes place after school enrolment. Very often comorbid anxiety disorders, especially social phobia and depression also occur. The course is very variable and with some affected persons regression of the pathology occurs suddenly and completely and with others there is a slow regression of the symptoms. Equally the disorder can persist until adulthood. Whilst formerly a traumatic genesis was assumed, a multifactorial etiology with genetic, psychological and language-associated effects is nowadays presumed. The therapy is supported through psychotherapy, speech therapy and psychopharmacology.