Endoscopic ultrasonography (EUS), which uses a high sonographic frequency (7.5 mHz) is a recently developed diagnostic tool that enables detailed analysis of the digestive wall and visualization of adjacent structures, like the posterior mediastinum through the esophagus. Thus, EUS may provide accurate documentation of the extent of esophagogastric malignancies, and of the adjacent lymph-node involvement. From now, results in preoperative staging compare favourably with CT scan. EUS provides also helpful complementary informations for the diagnosis of giant fold gastropathies or submucosal (or extrinsic) abnormalities. Moreover it may be usefull for the post-therapeutic follow-up of cancers, ulcers or varices.