Endoscopic ultrasonography (EUS) was performed in 10 patients with gastric non-Hodgkin lymphoma (NHL). EUS visualized hypoechoic intramural lesions with destruction of normal gastric wall architecture together with perigastric lymph node involvement. EUS was more accurate than endoscopy, barium meal, and computerized tomography scan in detecting and staging gastric NHL because of the high resolution. The non-resectability could reliably be diagnosed before surgery based on the detection of deep infiltration of the lesion into the surrounding tissues and/or organs EUS appears to be a sensitive diagnostic modality for detecting, staging, and following up after chemotherapy of gastric NHL. Technical improvements allowing ultrasonically guided biopsy or cytological puncture may further enhance its diagnostic usefulness.