Introduction. Among the factors that lead to the formation of cicatricial changes in the renal parenchyma are genetic ones. Data from the literature indicate a tendency toward increased production of the transforming growth factor (TGF-B1) [5, 10]. According to rare studies, polymorphism of the TGF-B1 gene occurs in 82% of patients with reflux-nephropathy [7].Objective to study: the effect of allelic polymorphisms of the gene TGF-B1 (-509 C / T, +869 T / C) on the course of pyelonephritis in young children.Materials and methods. In the work we used materials obtained during the survey of 100 young children with pyelonephritis. The first subgroup comprised 50 children with pyelonephritis on the background of vesicoureteral reflux and the second subgroup consisted of 50 children with pyelonephritis without evidence of vesicoureteral reflux. The control group consisted of 50 practically healthy children.Verification of the diagnosis was carried out on the basis of an in-depth examination according to the order of the Ministry of Health of Ukraine N. 627 of 03.11.2008. "On the treatment of children with urinary tract infections and tubulointerstitial nephritisResults of the study and their discussion:When comparing the distribution of genotypes and alleles of the polymorphism -509 of the TGF-B1 gene between the children of the main group and the comparison group, a significant increase in the frequency of carriers of the HS genotype in children of the main group (34 cases - 68 ± 4.86%) was observed compared to the frequency of the allele homo-carriers C in the comparison group (7 cases - 14 ± 1.41%), p T in position -509 of the TGF-B1 gene in the children of the main group, found that the frequency of secondary pyelonephritis of III degree of severity in the homozygotes of the mutant allele (80.1 ± 11.12%, 95% CI: 65 79 87.68) was significantly higher than in homozygotes of the main allele (10.01 ± 4.46%, 95% CI: 5.25-13.23) and heterozygotes (9.9 ± 2.51% 95% CI: 5.13 - 14.67), p T in the +869 position of the TGF-B1 gene in the children of the main group, the third degree of activity of the inflammatory process was significantly more likely to have carriers of the TT genotype (65.02 ± 6.74%, 95% CI: 52.72 - 74, 81%) compared with heterozygotes (19.97 ± 4.28%, 95% CI: 13.62 - 24.95%) and the allele C homocarriers (15.03 ± 2.71%, 95% CI: 8 59 - 19.42%), p <0.01.Conclusions:Thus, our studies have shown that children of early age, carriers of the genotype C-509C (34-68 ± 4.86%) and T + 869T (29-58 ± 4.46) are more likely to suffer from pyelonephritis against the background of vesicoureteral disease, ureter reflux than the heterozygotes C-509T (7-14 ± 1.13%) and T + 869T (13-26 ± 1.92%), as well as the homozygotes T-509T (9-18 ± 1.89%) and C 869C (8-16 ± 1.86%), p <0.01.In a significant majority of homozygotes C-509C (80,1 ± 11,12%) and T + 869T (65,02 ± 6,74%) there was pyelonephritis from the ІІІ century. activity of the inflammatory process.