ObjectivesPolymorphisms in base excision repair (BER) genes are associated with risk for several types of cancers but have not been studied with respect to endometrial cancer among Japanese women. Therefore, we conducted a case-control study to explore the association between polymorphisms in BER genes and the risk for endometrial cancer.Methods/MaterialsThis study included a total of 91 postmenopausal subjects with endometrial cancer and 261 controls without cancer who visited the Aichi Cancer Center between 2001 and 2005. We focused on single nucleotide polymorphisms within coding regions of 5 BER genes (OGG1,MUTYH,XRCC1,APEX1, andPARP1). To assess lifestyle in the etiology of endometrial cancer, we used a self-administered questionnaire. Associations were evaluated using multivariate unconditional logistic regression models. We also assessed whether there were intergenic associations or an interaction with obesity.ResultsWe observed a significant association between endometrial cancer risk andXRCC1rs1799782 (C > T, Arg194Trp) andXRCC1rs25487 (G > A, Arg399Gln). We uncovered a significant association between obesity (body mass index, ≥25) and rs25487. TheXRCC1polymorphisms were in complete linkage disequilibrium, and theXRCC1haplotype TG associated significantly with endometrial cancer risk. The interaction between the CA haplotype and body mass index was marginally significant, whereas interaction between haplotype inXRCC1and rs1136410 (PARP1) was not significant.ConclusionsWe found a significant association between endometrial cancer risk andXRCC1polymorphisms and haplotype TG in postmenopausal Japanese women.