Primary extranodal B cell lymphoma of mucosa- associated lymphoid tissue (MALT) can develop in diverse anatomic locations such as the stomach, salivary gland, thyroid, lung, and breast. Its distribution in the GI tract is as follows: 50∼60% in the stomach, 20∼30% in the small intestine and ileocecal area and 10% in the colorectal area. Although autoimmune and infectious diseases are known as the main etiologies, H. pylori infection has been clearly shown to play a causative role in lymphomagenesis, especially in the stomach. H. pylori eradication therapy only can induce disease remission nearly in 80% of the cases of gastric MALT lymphoma. However, there is lack of evidence for the extragastric area. In this case, a 71-year-old woman with low abdominal pain was diagnosed as having a rectal MALT lymphoma that was noted as a solitary rectal mass in a colonoscopic examination. Remission induction was commenced by H. pylori eradication and radiation therapy. (Korean J Gastrointest Endosc 2008;36:102-106)