The lack of significant differences in mean ALL onset age among MTHFR TT-homozygotes (WW/TT 4.7 ± 2.1, WD/TT 5.9 ± 3.9, and DD/TT 6.2 ± 3.4 years) confirmed, in turn, the contrasting effect MTHFR 677 variant carries out. This evidence concerns the gene MTHFR and acute lymphoblastic leukemia.