Oxidative stress has been implicated in etiopathogenesis of Graves' disease (GD). Increased lipid peroxidation and oxidative DNA damage have been found in GD patients. Oxidative DNA damage is mainly repaired by the base-excision repair (BER) pathway. Polymorphisms in DNA-repair genes have been associated with the increased risk of various diseases and could also be related to the etiology of GD. Therefore, we conducted a study including 197 patients with GD and age- and sex-matched 303 healthy subjects to examine the role of single-nucleotide polymorphisms of BER genes, APE/Ref-1 (codon 148) and XRCC1 (codons 194 and 399) as a risk factor for GD. These polymorphisms were determined by quantitative real-time PCR and melting curve analysis using LightCycler. No significant association was observed between the variant alleles of APE/Ref-1 codon 148 [odds ratio (OR) = 0.89, 95% confidence interval (CI) = 0.69-1.17], XRCC1 codon 194 (OR = 1.24, 95% CI = 0.79-1.94), and XRCC1 codon 399 (OR = 1.12, 95% CI = 0.86-1.46) and GD. These preliminary results suggest that APE/Ref-1 (codon 148) and XRCC1 (codons 194 and 399) polymorphisms are not significant risk factors for developing GD. Copyright (C) 2009 John Wiley & Sons, Ltd.