The majority of gastrointestinal lymphomas belongs to the group of the MALT (mucosa-associated lymphoid type) lymphomas arising in the stomach, therefore rendering them accessible to endoscopy. Staging currently follows the modified Ann Arbor classification but most likely in the future, the TNM-based Paris staging system will be applied due to its detailed description of the local spread as well as the extraintestinal dissemination. For assessment of gut wall infiltration and local lymphonodular involvement, endoscopic ultrasound currently represents the standard procedure and is an essential diagnostic tool regarding locoregional staging. Additionally, the method confers a high prognostic value regarding treatment response in MALT lymphoma. In endoscopic ultrasound stage EI 1, Helicobacter pylori eradication leads in 70 - 100 % to a complete response. However, the value of endoscopic ultrasound in the follow-up of lymphomas after chemotherapy remains elusive and controversial. There is no clear correlation between histologically proven residual disease and endosonographic results. Thus, so far, endoscopic ultrasound will not replace bioptic surveillance after MALT lymphoma treatment.