The analysis showed the sample size in recessive and dominant models, the tumor type in allelic, homozygous, and heterozygous models, and the ethnicity in allelic, homozygous, recessive, and dominant models could be important confounding factors for the association between the HNC risk and CYP1A1 MspI polymorphism (P < 0.05). The gene discussed is CYP1A1; the disease is neoplasm.