Endoscopic ultrasonography of the digestive tract provides for a precise ultrasonic study of the accessible gastrointestinal walls (oesophagus, stomach, duodenum, rectum) and, through these walls, of the adjacent organs (lymph node clusters, posterior mediastinum, pancreas, extrahepatic biliary ducts and perirectal environment). This method is better than computerized tomography to evaluate the local and regional extension of oesophageal and cardial carcinomas producing little or no stenosis and of gastric and rectum carcinomas and lymphomas. It is the examination of choice to detect a peri-anastomotic recurrence of these cancers and to evaluate submucosal tumors of the digestive tract. This method, without morbidity is better than computerized tomography or ultrasonography in the aetiological diagnosis of obstacles in the biliary tract and in the diagnosis and pretherapeutic assessment of pancreatic cancers or endocrine tumors.