The causative association between Helicobacter pylori and gastric mucosal inflammation is well established. The inflammatory process leads to the acquisition of mucosa-associated lymphoid tissue (MALT) by the stomach. Evidence links H. pylori gastritis with the development of low-grade primary gastric lymphoma with a phenotype specific for lymphoma of MALT type. It is now accepted that primary low-grade MALT lymphomas regress with H. pylori eradication therapy. However, the response of primary, diffuse, large-cell gastric lymphoma to H. pylori eradication therapy is still not established. We report a case of a primary high-grade gastric lymphoma regressing after H. pylori eradication therapy.