Mucosa-associated lymphoid tissue (MALT) lymphoma is a common low grade B-cell lymphoma arising from a background of chronic inflammatory disease at a number of mucosal sites. Those originating in the stomach are causatively linked to Helicobacter pylori infection and eradication of the bacterium with antibiotics leads to long-term complete regression of the lymphoma in ~70% of cases. Now, there is further evidence of linking Campylobacter jejuni, Borrelia burgdorferi and Chlamydia psittaci infection with immunoproliferative small intestine disease, MALT lymphoma of the skin and ocular adnexa respectively. t(11;18)/API2-MALT1, t(1;14)/IGH-BCL10, t(14;18)/IGH-MALT1 and t(3;14)/IGH-FOXP1 occur at considerably variable incidences in MALT lymphomas of different sites. The first three chromosome translocations are specifically associated with the MALT lymphoma entity and the oncogenic products of these translocations have been shown to target a common molecular pathway, i.e. the nuclear factor-κB pathway. Here, I review the recent advances in our understanding of the association of microbial pathogens with MALT lymphoma of various sites and the molecular genetics underlying the lymphoma development. [J Clin Exp Hematopathol 47(2) : 31-42, 2007]