Ultrasonography has become widely accepted as a diagnostic tool for gastrointestinal diseases. It not only assesses the lumen but more importantly also the wall and the surrounding structures of the stomach and bowel. Furthermore, functional processes (peristalsis, blood flow) can be visualised and provide important information for passage and perfusion. Modern high resolution (compressive) sonography represents an ideal complementary method besides endoscopy for the gastroenterologist. It is used in emergency diagnosis in cases of acute appendicitis and peridiverticulitis. Here sonography is the method of first choice achieving a high sensitivity. The same applies to ileus, which can be diagnosed significantly earlier by sonography than with conventional X-ray methods. Meanwhile sonography can contribute considerable information to clarify pathogenesis (e. g., invagination, intususception). The detection of a perforation depends strongly on the competence of the examiner. The main advantage is the detection of a covered perforation and the genesis (e. g., ulcer). Ultrasound is less commonly considered in celiac sprue but important complementary information can be obtained. Advanced tumours of the gastrointestinal tract can easily be visualised, although early stages can hardly be detected by means of sonography. An accurate T-staging of tumours is not possible with transabdominal sonography, not least because some parts of the bowel (colon and rectum) cannot always and completely be seen. Exclusion of tumour or early detection is not possible by ultrasound. In intestinal diseases additional information besides clinical and endoscopic aspects can be achieved by ultrasound. Sonography is important for differential diagnosis and follow-up and spares the patient from more incriminatory endoscopic operations. Ultrasound is equal to other imaging methods in detecting complications (fistulas, abscess, stenosis). Due to the complexity of the topic the following review will concentrate on giving an idea of the present status of sonography in chronic inflammatory bowel disease, some less frequent intestinal infections (bacterial, pseudomembranous, neutropenic colitis, intestinal tuberculosis), the ischaemic bowel diseases as well as diseases of the upper gastrointestinal tract.