Functional disroders are the most important cause for complaints in the gastrointestinal tract. Dysfunction may concern one or more physiologic properties like tonus, motility, secretion, sometimes also resorption and digestion, or their interaction. Functional disorders of the esophagus (esophagospasm and achalasia) become manifest as dysphagia. Halitosis, bad taste, burning tongue, and flatulent abdomen are frequent symptoms of functional disorders of the gastrointestinal tract. Irritable bowel syndrome is probably the functional disorder most freqently found in the gastrointestinal tract. Characteristic symptoms are pain in the lower and upper middle abdominal region, obstipation and/or diarrhea, flatulent abdomen, mucous discharge with the stools and urgent defecation with cramps relieved after discharge. Prognosis quoad vitam is good, the course, however, is subject to many changes. Therapie is symptomatic. Diagnostic and psychotherapeutic measures are intended to help remove carcinophobia and to overcome conflicts and fears.