XRCC1 and head and neck squamous cell carcinoma: There was significant association between XRCC1 Arg194Trp polymorphism with HNSCC risk based on oral cavity tumor site under heterozygous and dominant models (p values <.05); the Arg/Trp + Trp/Trp (CT + TT) genotypes were significantly associated with increased risk of HNSCC development compared to Arg/Arg (CC) genotype (dominant model); also, the Arg/Trp variant significantly increased the HNSCC risk compared to Arg/Arg (heterozygous model); the associations were not significant under other genetic models (p value >.05).