THE AIM. To determine the concentration of natriuretic peptide in the blood serum in children with congenital malformations of the urinary system (CM US) and to compare with the activity of renin-angiotensin-aldosterone system (RAAS).MATERIALS AND METHODS.119 patients with CM US aged 3 to 18 years were examined. A control group of 10 clinically healthy children. 3 groups were assigned: group I – 55 children with congenital vesicoureteral reflux, and group II – 34 children with congenital hydronephrosis and ureterohydronephrosis, III group – 30 children with other forms of dysembryogenesis of the US. Following indicators were identified by ELISA in the blood: renin, aldosterone, N – terminal propeptide natriuretic hormone (NT-рroВNР). RESULTS.NT-рroВNР, renin and aldosterone hyperproduction were diagnosed in 59,6%, 69,7%, 54.6 % of sick children relatively. Concentrations were higher in all variants of malformations in comparison with the control group. Significant differences were revealed in obstructive species, where arterial hypertension (AH) was diagnosed more often. Patients with AH recorded significantly higher concentrations of NT-proВNР and renin.CONCLUSION.The key point in pathological processes developmentand progression in the cardiovascular system and kidneys is the activation of RAAS. The system of natriuretic factors is important in maintaining the compensated state of patients due to the blockade of RAAS.