Aim. To estimate the urinary excretion of KIM-1 in groups of patients with varying clinical activity of chronic glomerulonephritis (CGN) and to determine the possibility of using the urinary KIM-1 concentration as a criterion for predicting the course of CGN. Subjects and methods. A total of 47 patients with CGN were examined. Group 1 included 10 patients with nephrotic syndrome (NS) and decreased glomerular filtration rate (GFR); Group 2 consisted of 16 patients with NS and normal GFR; Group 3 comprised 10 patients with partial remission of NS; Group 4 included 11 patients with CGN, hematuria, moderate proteinuria, and normal GFR. A control group consisted of 9 healthy individuals. In the examined groups, urinary KIM-1 concentrations were estimated using an indirect immunoassay. Results. The urinary KIM-1 excretion in the patients with CGN was higher than that in the healthy individuals (p <0.0001), at the same time, in the average the KIM-1 excretion was statistically significantly higher in the patients with proteinuria than in those with hematuria (p=0.01). The highest levels were registered in Group 1; Group 2 was intermediate in the level of KIM-1 excretion and the difference between Groups 3 and 4 proved to be statistically insignificant. The lowest levels were noted in Group 4 and in the controls; the differences between the groups were statistically insignificant. In the patients with CGN, the level of KIM-1 excretion was established to correlate with all indicators of NS severity. The value of the determination of KIM-1 as a risk factor of persistent/refractory NS was estimated. The results of constructing the ROC-curve indicate that KIM-1 levels higher than 2.34 ng/ml could predict NS persistence in CGN patients with a high sensitivity and specificity. Conclusion. Urinary KIM-1 levels may be used to estimate the activity of CGN with NS and to evaluate the efficiency of treatment. The results of the study substantiate the search for ways of pharmacological blockade of KIM-1 production in the kidney in order to optimize the methods that impact on the pathogenesis of CGN progression.