Mucosa-associated lymphoid tissue (MALT) showing a follicular structure can develop in the gastric mucosa as a response to Helicobacter pylori infection. We emphasize the importance of anti-H. pylori antibiotic therapy in the elimination of acquired MALT. Of the 200 patients studied, acquired MALT was found in 70 of the 151 H. pylori-positive patients, whereas it was present in only five of the 49 H. pylori-negative patients. Thirty-eight H. pylori-positive and MALT-positive patients were treated with antibiotic therapy and reevaluated after 6 months: 21 patients were H. pylori negative/MALT negative, 12 were H. pylori positive/MALT positive, four were H. pylori negative/MALT positive, one was H. pylori positive/MALT negative. In the control group (n = 20), H. pylori and acquired MALT were still present at follow-up. One patient with histological and immunohistochemical evidence of low-grade B-cell gastric MALT lymphoma underwent antibiotic treatment and was reexamined after 8, 12, and 24 weeks: histological examination of biopsy samples showed regression of the MALT lymphoma in tandem with the disappearance of H. pylori colonization. Our data confirm the correlation between H. pylori infection and acquired MALT, as documented by the ability of antibiotic therapy to induce the disappearance of acquired MALT and regression of MALT lymphoma. Considering the potential evolution of MALT into low-grade B-cell MALT lymphoma, H. pylori eradication should play a role in the prevention of this tumor.