BACKGROUND Acute lymphocytic leukemia (ALL) in children is a clonal disease of bone marrow hematopoietic stem cells. This study aimed to explore the associations between MTHFR or TS genetic polymorphisms and susceptibility to acute lymphocytic leukemia (ALL) in children. MATERIAL AND METHODS This case-control study included 79 ALL patients (case group) and 102 non-ALL patients (control group). Post-PCR genomic DNA sequencing revealed MTHFR C677T and MTHFR A1298C genotypes and TS polymorphisms. The χ² test was used to compare differences in MTHFR and TS polymorphisms (including genotypic and allelic distributions) between groups. Logistic regression analysis was used to determine genetic polymorphisms and ALL risk associations. RESULTS The results indicated that TS 3R allele frequency was significantly higher in the case group than in the control group (χ²=7.45, P<0.05). The MTHFR C677T and MTHFR A1298C polymorphisms were not associated with ALL risk. Compared to the TS 2R/2R genotype, subjects carrying TS 2R/3R were twice as likely to develop ALL, and the TS 3R/3R+3R/4R genotype carried a 4-fold higher risk of developing ALL (OR=1.96, CI: 1.14-3.36). CONCLUSIONS The TS genetic polymorphisms increase the ALL risk. The TS 3R allele was a risk factor for ALL. There were no associations between MTHFR C677T or MTHFR A1298C polymorphisms and ALL susceptibility.