Background/Aims: Rats with subtotal nephrectomy (5/6NPX) rapidly develop systemic hypertension and proteinuria. The aim of our study was to evaluate the changes in oxidative stress parameters after 2 and 4 weeks of treatment with renin-angiotensin system (RAS)-blocking agent losartan and beta-blocking agent atenolol in experimental chronic renal failure (CRF). Methods: After 5/6NPX, rats were immediately treated with losartan or atenolol. The lipid peroxidation (LPO) products malondialdehyde and 4-hydroxyalkenals and oxidized and reduced glutathione values were measured in the renal cortex tissue and in blood; isoprostanes in urine. Results: There were no differences in the blood pressure values, serum creatinine levels or in daily proteinuria using both antihypertensive treatments. Losartan treatment lowered significantly LPO in kidney tissue after 2 and 4 weeks of treatment compared with untreated and atenolol-treated animals and induced the decrease of excretion of isoprostanes in urine at the end of the study. There was no ameliorating impact of losartan or atenolol observed in the blood status of oxidative stress in this period of time. Conclusion: In the early period of experimental CRF, losartan treatment but not atenolol treatment induces significant decline in LPO grade in the kidney tissue of nephrectomized rats. RAS blockade in the kidney influences local tissue LPO in a much greater extent than in blood.