Compared with people carrying AA allele of MTHFR rs1801133, a higher risk of childhood leukemia may occur in people carrying AG+GG allele of MTHFR rs1801133 with a younger age (<15 years; OR=1.23, 95%CI=1.09–1.97, P=0.014) or complete remission (OR=1.58, 95%CI=1.29–2.39, P=0.004). The gene discussed is MTHFR; the disease is leukemia.