To evaluate the potential value of endoscopic ultrasonography in primary gastric lymphoma, we compared endoscopic ultrasonography findings with endoscopic and histologic findings in 15 patients in whom the diagnosis had been established by radiography and endoscopy, including forceps biopsy. The patients were divided into four groups according to the endoscopic ultrasonography findings. The groups included the following: superficially spreading type (six patients), diffusely infiltrating type (three patients), mass-forming type (four patients), and mixed type (two patients). The endoscopic ultrasonography findings correlated well with the endoscopic, macroscopic, and histologic findings. The histologic findings in nine patients with the endoscopic ultrasonography superficially spreading type or diffusely infiltrating type revealed B-cell lymphoma arising from mucosa-associated lymphoid tissue, which shows slowly infiltrative growth. In four patients with the endoscopic ultrasonography mass-forming type, on the other hand, the tumor histologic finding consisted of diffuse large-cell or diffuse mixed-cell type. Our results indicate that endoscopic ultrasonography may provide information helpful for the management of primary gastric lymphoma.