The presence of lymphoid tissue in the gastric mucosa is virtually pathognomonic of Helicobacter pylori infection. This lymphoid tissue has mucosa–associated lymphoid tissue (MALT) characteristics suggesting that H. pylori infection may represent a stimulus for the growth of gastric MALT lymphoma. H. pylori can be detected in more than 90% of patients with low–grade gastric MALT lymphoma supporting the aetiological role of the organism. The strongest evidence for the significance of H. pylori in the pathogenesis of low aetological–grade gastric MALT lymphoma is provided by clinical studies showing that cure of H. pylori infection is followed by a complete regression of these tumours in most patients. This paper reviews the current knowledge about antibacterial treatment of low–grade gastric MALT lymphoma, and immunological and molecular aspects in the pathogenesis of the disease.