The results of numerous studies in recent years proved the indisputable role of oxidative stress as an important factor in the pathogenesis of microvascular complications of diabetes. This study involved determining the state of prooxidant-antioxidant balance as a marker of oxidative stress in patients with type 2 diabetes mellitus with nephropathy, depending on the functional state of the kidneys. 76 patients with diabetic nephropathy, 22 patients with hypertension and 20 healthy individuals (control) were examined. The prooxidant-antioxidant balance of blood serum was calculated as the ratio of total hydroperoxides and total antioxidant activity. The content of total hydroperoxides and total antioxidant activity was determined by colorimetric method. The results of the study showed a significant prooxidant-antioxidant balance increase in patients with diabetic nephropathy when compared with the control group and hypertensive subjects. We established that the progression of chronic kidney disease is accompanied by markeable prooxidant-antioxidant balance increase in patients with reduced glomerular filtration rate. A direct correlation between prooxidant-antioxidant balance and glycosylated hemoglobin and negative correlation with glomerular filtration rate was found. The data obtained indicate the relationship between prooxidant-antioxidant balance, renal function and diabetes compensation parameters. Prooxidant-antioxidant balance elevation may be considered as a risk factor for the development and progression of kidney disease in type 2 diabetes. Preservation of optimal prooxidant-antioxidant balance may be considered as a potential target for therapy aimed at reducing the rate of progression of renal lesions in type 2 diabetic patients. Keywords: prooxidant-antioxidant balance, diabetes mellitus, diabetic nephropathy.