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8-hydroxydeoxyguanosine (8-OHdG) is the most frequent oxidative DNA damage. 8-oxo-deoxyguanosine DNA glycosylase 1 (OGG1) is involved in the repair of 8-OHdG. Many studies indicated that DNA repair is decreased in type 2 diabetes (T2DM). Single nucleotide polymorphisms in DNA repair genes may be linked to a decrease in DNA repair activity. The main objective of this study was to see how the OGG1 Ser326Cys gene polymorphism affected OGG1 expression and urinary excretion of 8-OHdG in T2DM patients. OGG1 expression and OGG1 genotyping in lymphocytes were detected by immunocytochemical staining and Polymerase Chain Reaction-Restriction Fragment Length Polymorphism assay, respectively. Urinary 8-OHdG levels were measured by using ELISA kit in patients with T2DM. Compared with control cases, patients with T2DM had lower OGG1 immunopositivity and higher urinary 8OHdG levels. No significant difference was found in OGG1 immunopositivity or urinary 8-OHdG levels between subjects with different OGG1 genotypes in both groups. In conclusion, The OGG1 Ser326Cys gene polymorphism has no effect on neither OGG1 expression nor urinary 8-OHdG levels. Increased urinary 8-OHdG levels despite low OGG1 immunopositivity may be derived from the action of other DNA repair enzymes.