Abstract Background: The molecular mechanism associated with remission of primary gastric lymphoma post helicobacter pylori eradication is still unclear. Aim of the study: to evaluate Microsatellite (MSI) instability at markers adjacent to Chromosomal loci involved in primary gastric lymphoma in relation to helicobacter eradication therapy. Methods: 107 primary gastric lymphoma patients included 30 low grade Mucosa Associated Lymphoid Tissue Gastric lymphoma (MALT), 36 Diffuse large gastric lymphoma with MALT component (MALTDLBCL) and 41 DLBCL gastric lymphoma (DLBCL) were treated with anti Helicobacter pylori therapy as fi rst line treatment and to asses for Microsatellite instability (MSI) Results: the incidence of complete remission post helicobacter pylori eradication was higher in Low grade MALT in comparison to MALTDLBCL and denovo DLBCL. The incidence of MSI is decrease post helicobacter pylori eradication in all subtypes Conclusion: Remission of gastric lymphoma post Helicobacter eradication may associate with correction of MSI