Objective - The aim of the work was to study the contribution of the immune response mediator genes polymorphism (TNFA rs1800629, LTA rs909253, IL1B rs16944, IL2-IL21 rs6822844, IL2RA rs2104286, IL6 rs1800795, IL10 rs1800872, MIF rs755622, CTLA4 rs3087243, NFKB1 rs28362491, PTPN22 rs2476601, PADI4 rs2240336) to the formation of the predisposition to juvenile idiopathic arthritis (JIA) and its clinical variants. Material and Methods - The JIA group included 330 patients and the control group - 342 volunteers without autoimmune diseases from the Republic of Bashkortostan, Russia. Genotyping was conducted by the real-time polymerase chain reaction. Results - Taking into account the differences by sex, it was established, that the alleles/genotypes of the TNFA rs1800629, LTA rs909253, IL2-IL21 rs6822844, PTPN22 rs2476601 polymorphic loci and the TNFA rs1800629*G - LTA rs909253*G haplotype are associated with the development of JIA as a whole (p<0.05); alleles/genotypes of the LTA rs909253, IL1B rs16944, IL2-IL21 rs6822844, IL2RA rs2104286, IL6 rs1800795, IL10 rs1800872, MIF rs755622, CTLA4 rs3087243, NFKB1 rs28362491, PTPN22 rs2476601 polymorphic loci and the TNFA rs1800629*G - LTA rs909253*G haplotype - with some of JIA clinical variants (p<0.05). Conclusion - In this work, the relationship of the alleles, genotypes and haplotypes of a number of the immune response mediator genes polymorphic loci with the risk of the development of JIA and its clinical variants was established. Specific associations were observed for girls and boys, which indicates the existence of sexual dimorphism in the JIA pathogenesis.