Background- Catheter-based renal sympathetic denervation (RDN) reduces office blood pressure (BP) in patients with resistant hypertension according to office BP. Less is known about the effect of RDN on 24-hour BP measured by ambulatory BP monitoring and correlates of response in individuals with true or pseudoresistant hypertension. Methods and Results-A total of 346 uncontrolled hypertensive patients, separated according to daytime ambulatory BP monitoring into 303 with true resistant (office systolic BP [SBP] 172.2±22 mm Hg; 24-hour SBP 154±16.2 mm Hg) and 43 with pseudoresistant hypertension (office SBP 161.2±20.3 mm Hg; 24-hour SBP 121.1±19.6 mm Hg), from 10 centers were studied. At 3, 6, and 12 months follow-up, office SBP was reduced by 21.5/23.7/27.3 mm Hg, office diastolic BP by 8.9/9.5/11.7 mm Hg, and pulse pressure by 13.4/14.2/14.9 mm Hg (n=245/236/90; P for all <0.001), respectively. In patients with true treatment resistance there was a significant reduction with RDN in 24-hour SBP (-10.1/-10.2/-11.7 mm Hg, P<0.001), diastolic BP (-4.8/-4.9/-7.4 mm Hg, P<0.001), maximum SBP (-11.7/-10.0/-6.1 mm Hg, P<0.001) and minimum SBP (-6.0/-9.4/-13.1 mm Hg, P<0.001) at 3, 6, and 12 months, respectively. There was no effect on ambulatory BP monitoring in pseudoresistant patients, whereas office BP was reduced to a similar extent. RDN was equally effective in reducing BP in different subgroups of patients. Office SBP at baseline was the only independent correlate of BP response. Conclusions-RDN reduced office BP and improved relevant aspects of ambulatory BP monitoring, commonly linked to high cardiovascular risk, in patients with true-treatment resistant hypertension, whereas it only affected office BP in pseudoresistant hypertension. CLINICAL TRIAL REGISTRATION - : URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00664638 and NCT00888433.