The magnitude of association between cigarette smoking and oral cancer was higher in individuals with a SULT1A1*1 isoform (wild type, genotype Arg/Arg) (OR = 10.19, 95% CI = 3.90–26.61) than in those with at least one SULT1A1*2 allele (genotypes Arg/His + His/His) (OR = 4.50, 95% CI =2.09–9.69). This evidence concerns the gene SULT1A1 and lip and oral cavity carcinoma.