Personalized medicine means the selection of therapy for patients, taking into account the assessment of genetic risk factors for side effects. A number of studies show that folate metabolism disorders, including single nucleotide polymorphisms (SNPs) in the genes of folate-metabolizing enzymes, are more frequently detected in schizophrenic patients than in the general population. The role of SNPs of the key folate cycle enzymes in developing the extrapyramidal side effects of antipsychotics has not yet been studied, although there is evidence of their association with other movement disorders.Objective: to analyze the association between the carriage of SNP alleles of MTHFR 677C>T, MTR 2756A>G, and MTRR 66A>G and the severity of extrapyramidal side effects of antipsychotics in patients with schizophrenia.Patients and methods. The investigation included 61 patients with schizophrenia (according to the criteria for ICD-10 Code F20). All the patients took antipsychotics for at least 7 hospital days were examined using real-time polymerase chain reaction (PCR) with allele-specific primers, followed by detection for the carriage of SNP alleles of MTHFR 677C>T, MTR 2756A>G, and MTRR 66A>G. The standardized Simpson–Angus scale (SAS) was used to evaluate the severity of extrapyramidal symptoms; the PCR test results were unknown during their examination.Results and discussion. In the patients carrying a low-functional 677 T allele in the gene of the key folate cycle enzyme MTHFR, the severity of extrapyramidal side effects of antipsychotics was statistically significantly higher than in the carriers of the wild-type genotype: 13.27±5.10 versus 9.84±6.03 SAS scores, respectively (t=-2.40; p=0.020). In addition, the carriage of the wild allele A of SNP in the MTRR 66A>G gene (F=3.83; p=0.0283; pcorr.=0.043) is associated with the severity of extrapyramidal symptoms. There was a direct moderate correlation of the number of risk alleles at two loci with the total SAS score (r=0.51; p=0.00017).Conclusion. The polymorphic allele of MTHFR 677T and the wild allele of MTRR 66A can be regarded as risk alleles for the development of extrapyramidal side effects of antipsychotics.