It was only the endoscopic ultrasonography that allowed the esophagus and posterior mediastinum to be accessible to ultrasonography. The esophageal wall may be presented in its different anatomic layers to a degree of precision unattained by any other imaging procedure. Being important in the esophagus, both the upper rim of the tumor and the infiltration depth can this way be prognosed correctly to about 85%. In consequence, this allows proceedings appropriate to the tumor stage within the bounds of a multimodal therapeutic concept of esophagus carcinomas. Impressions of the esophagus caused by mediastinal tumors are safely distinguished from intramural tumors. Multiple biopsies to get an examination specimen from a deeper layer should be performed under no other conditions than after endoscopic ultrasonographic examination and just for special questions. In the differential diagnosis of achalasia and peptic stenosis of the esophagus, endoscopic ultrasonography proved to be less efficient. As for bronchial carcinomas, conclusive hints may be drawn from transesophageal and intratracheal ultrasonography. However, due to limited possibilities of judgment caused by air-containing structures these methods are not firmly established in the preoperative staging.