This 12-week, multicenter, randomized, double-blinded, 4-arm study in 440 patients with moderate to severe hypertension compared ambulatory blood pressure (ABP) responses with a triple-combination regimen (olmesartan medoxomil [OM] 40mg, amlodipine besylate [AML] 10mg, and hydrochlorothiazide [HCTZ] 25mg) and its component dual-combination regimens at similar doses. At week 12, the triple combination resulted in a greater reduction in mean 24-hour systolic and diastolic blood pressure (-30.3/-18.0mmHg) compared with the 3 dual-combination regimens (OM 40 mg/AML 10mg: -23.5/-13.9, OM 40 mg/HCTZ 25mg: -23.9/-14.5, and AML 10 mg/HCTZ 25mg: -18.5 mm Hg/-10.7mmHg; P<.0001 each). Greater efficacy was also found during daytime and nighttime hours and during the last 6, 4, or 2hours of the dosing interval. The authors conclude that the triple combination of OM 40 mg/AML 10 mg/HCTZ 25mg demonstrated superior efficacy and sustained reductions in ABP compared with its dual-combination components. © 2011 Wiley Periodicals, Inc.