Background: RNAi therapeutics targeting angiotensinogen (AGT) lower blood pressure in animal models of essential hypertension, but whether this treatment is beneficial in hypertensive chronic kidney disease (CKD) is yet unknown. Our aim was to assess the effectiveness of a small interfering RNA (siRNA) targeting hepatic AGT in a rat model of hypertensive CKD. Methods: Sprague Dawley rats (n=7-12 per group) were subjected to 5/6th nephrectomy, allowed to recover for four weeks, and subsequently subjected to one of five treatments: (1) vehicle, (2) AGT siRNA (10-30 mg/kg, s.c. every 2 weeks), (3) AGT siRNA + losartan (30 mg/kg/d), (4) losartan (30 mg/kg/d), or (5) losartan + captopril (30 and 6 mg/kg/d). Mean arterial pressure (MAP) was measured by radiotelemetry for 4 weeks, glomerular filtration rate (GFR) was measured by transcutaneous FITC-sinistrin clearance. Results: AGT siRNA and AGT siRNA + losartan reduced plasma AGT by 96.5 ± 1.4% and 97.0 ± 2.3%, respectively. Over the course of 4 weeks, proteinuria increased with vehicle and this increase was abrogated by all treatments (Δ proteinuria at 4 weeks versus baseline: +0.17 [0.12, 0.23], +0.02 [-0.04, 0.05], -0.01 [-0.07, 0.06], -0.05 [-0.12, 0.00], -0.01 [-0.06, 0.11] for vehicle, AGT siRNA, AGT siRNA + losartan, losartan, losartan + captopril, P < 0.05 for all groups compared with vehicle). Similarly, heart weight was equally reduced by all treatments except vehicle. No intervention affected GFR. Over the course of 4 weeks, MAP increased (from a baseline of 154 ± 18 mmHg) during vehicle treatment and this rise was prevented by AGT siRNA (+13 ± 15 mmHg vs. -2 ± 14 mmHg, P > 0.05 for difference between groups). Combination treatment with AGT siRNA + losartan, losartan + captopril, and losartan alone caused a similar and marked reduction in MAP (-17 ± 14 mmHg, -21 ± 17 mmHg, and -33 ± 20 mmHg, P < 0.05 versus vehicle for all; differences between groups not significant). Conclusion: In experimental CKD, AGT siRNA monotherapy appears to reduce proteinuria and heart weight in a blood pressure-independent fashion, to a similar degree as losartan or combination treatment. Thus, an siRNA targeting hepatic AGT may be a potential therapeutic approach for providing renal and cardioprotection in CKD.