Endoscopic ultrasonography was performed in 8 patients with non-Hodgkin lymphoma of the stomach. Findings consisted of intramural infiltration or mucosal alteration together with perigastric lymph nodes, or both. Lymph node involvement was suggested by the presence of inhomogeneous hypoechoic echopatterns with clearly demarcated borders. Endoscopic ultrasonography was more accurate than computed tomography scan in the detection of transmural extent of malignancy and adjacent lymph node involvement. Because of the limited penetration depth of endoscopic ultrasonography, approximately 10 cm, more distant lymph nodes might be more clearly detected with computed tomography scan. Endoscopic ultrasonography was also more accurate than endoscopy and barium meal in the assessment of gastric wall infiltration. The resectability of gastric non-Hodgkin lymphoma was reliably detected by endoscopic ultrasonography before surgery. Endoscopic ultrasonography appears to be a sensitive diagnostic modality for detection, staging, and follow-up in gastric non-Hodgkin lymphoma. Technical improvements may further enhance the diagnostic value of this new procedure.