Chronic pyelonephritis is one of the most common diseases complicating numerous urologic pathologies or occurring as an independent pathology. Chronic pyelonephritis due to insufficient and often non-effective management might cause renal failure, even after risk factors removal. New approaches in chronic pyelonephritis management required. According to publications bone-marrow mesenchymal stem cells can improve chronic inflammation because of cytokine complexes secretion. Experimentally chronic pyelonephritis was simulated in 20 rats, after renal functional disorders were obtained (serum creatinine and urea concentration increase, creatinine clearance and sodium and calcium reabsorbtion decrease) 2 millions of fetal bone-marrow mesenchymal stem cells (first group) or 0.1 ml of saline (second group, control) were injected into the renal parenchyma. In the first group inflammation activity reduce after 2 weeks and all renal functional indicators improvement after two months were observed. In second group inflammation changes in urinalysis and functional disorders were persistent. Reliable decrease of concentrations of IgG and C3-component of complement were revealed in rats with chronic pyelonephritis, but after stem cells injections those concentrations returned to normal values. Histological assessment showed focal reduction of renal interstitial tissue histiolymphocytic infiltration compared to control group.