Objective of investigation: to study the role of Toll-like receptor 4 Asp299Gly gene polymorphism in the implementation of susceptibility to chronic pyelonephritis, to analyze its association with the major manifestations of the disease and to assess the impact on the synthesis of interleukin-6 in the blood of sick children.Methods. We examined a group of children aged 1–15 years with chronic pyelonephritis in the active stage (n = 60). Control group consisted of 95 apparently healthy people. Results. There were revealed significantly higher prevalence of Toll-like receptor 4 Asp299Gly gene polymorphism among children with chronic pyelonephritis (n = 60), identified a statistically significant correlation of mutant genotypes Asp299Gly, Gly299Gly with manifestation of the disease before the age of 3, and frequent episodes of acute respiratory viral infections, torpid urinary syndrome, unstable remission and increased secretion of interleukin-6 (p < 0.001). Thus, genetically determined Toll-like receptor 4 Asp299Gly gene polymorphism is a marker of high risk of early manifestation of chronic inflammation in the kidney interstitium and prolonged recurrent clinical course of the disease in children.