© 2014 by the American College of Cardiology Foundation. BACKGROUND Prior studies of catheter-based renal artery denervation have not systematically performed ambulatory blood pressure monitoring (ABPM) to assess the efficacy of the procedure. OBJECTIVES SYMPLICITY HTN-3 (Renal Denervation in Patients With Uncontrolled Hypertension) was a prospective, blinded, randomized, sham-controlled trial. The current analysis details the effect of renal denervation or a sham procedure on ABPM measurements 6 months post-randomization. METHODS Patients with resistant hypertension were randomized 2:1 to renal denervation or sham control. Patients were on a stable antihypertensive regimen including maximally tolerated doses of at least 3 drugs including a diuretic before randomization. The powered secondary efficacy endpoint was a change in mean 24-h ambulatory systolic blood pressure (SBP). Nondipper to dipper (nighttime blood pressure [BP] 10% to 20% lower than daytime BP) conversion was calculated at 6 months. RESULTS The 24-h ambulatory SBP changed -6.8 ± 15.1 mm Hg in the denervation group and -4.8 ± 17.3 mm Hg in the sham group: difference of -2.0 mm Hg (95% confidence interval [CI]: -5.0 to 1.1; p = 0.98 with a 2 mm Hg superiority margin). The daytime ambulatory SBP change difference between groups was -1.1 (95% CI: -4.3 to 2.2; p = 0.52). The nocturnal ambulatory SBP change difference between groups was -3.3 (95 CI: -6.7 to 0.1; p = 0.06). The percent of nondippers converted to dippers was 21.2% in the denervation group and 15.0% in the sham group (95% CI: -3.8% to 16.2%; p = 0.30). Change in 24-h heart rate was -1.4 ± 7.4 in the denervation group and -1.3 ± 7.3 in the sham group; (95% CI: -1.5 to 1.4; p = 0.94). CONCLUSIONS This trial did not demonstrate a benefit of renal artery denervation on reduction in ambulatory BP in either the 24-h or day and night periods compared with sham (Renal Denervation in Patients With Uncontrolled Hypertension [SYMPLICITY HTN-3]; NCT01418261).