Girls performed the vast majority of patients with urinary system infections. The prevalence of acute disease and specific gravity of chronic kidney impartments have been increasing with the age and were often accompanied with concomitant urological, gynecological and sexual pathologies. The purpose of the work was to determine the etiological and clinical preconditions of relapse and chronic pyelonephritis in girls. Materials and methods. An analysis of the clinical course of187 cases ofpyelonephritis in girls of the age of1 - 18 years had been performing in period from 2008 to 2018 years. The 60 patients in observed group had acute process and 127 ones were with the chronic course of the disease. Rresults. E. coli was the main etiological factor of the inflammatory process in kidneys. Thus, cases of acute and chronic pyelonephritis composed 63,5% and 44,2% in observed group appropriately. Furthermore, the proportion of grampositive flora increased in the cases of chronic pyelonephritis. In addition, almost 56,7% ofall girls with pyelonephritis had sexually transmitted infections, more likely the patients with chronic forms of the disease (69,3% and 30,0%, respectively (p