Overall, CYP1A1 rs4646903 polymorphism was closely associated with the increased risk of oral cancer according to the pooled ORs (CC vs TT: OR 1.65, 95% CI 1.33–2.05; CC vs TC+TT: OR 1.77, 95% CI 1.48–2.11; C vs T: OR 1.17, 95% CI 1.07–1.28). This evidence concerns the gene CYP1A1 and lip and oral cavity carcinoma.