OBJECTIVES: I. Determine the rate of eradication of Helicobacter pylori using omeprazole, colloidal bismuth subcitrate, tetracycline, and metronidazole in patients with low grade gastric lymphoma. II. Determine the macroscopic/endoscopic and microscopic healing/remission rate after eradication of Helicobacter pylori in this patient population. III. Determine the natural history of low grade gastric lymphoma after eradication of Helicobacter pylori.