Persistent somatic symptoms, somatoform disorders, functional somatic syndromes … The field of somatic symptoms which are associated with emotional distress and which can be more or less medically explained has produced a—sometimes confusing—variety of technical terms. The clarification and delineation of these terms and diagnostic concepts is a necessary prerequisite for understanding the patient’s underlying problem and for developing a promising treatment plan. To this end, the first three sections of the first chapter provide assistance: First, with the help of two case studies, an insight is given into the versatility of persistent somatic symptoms and accompanying psychological and coping problems in affected patients. This is followed by a summary of the historical development of the concept of persistent somatic symptoms. Diagnostic classification criteria and procedures are then presented, as well as assistance with differential diagnosis. The first chapter is rounded off with a summary of epidemiological facts on persistent somatic symptoms.