Most patients with hypertension require combination therapy in order to achieve blood pressure (BP) goals. This 40-week open-label extension of the 12-week double-blind Triple Therapy With Olmesartan Medoxomil, Amlodipine, and Hydrochlorothiazide in Hypertensive Patients Study (TRINITY) evaluated the efficacy and safety of triple-combination treatments with olmesartan medoxomil, amlodipine besylate, and hydrochlorothiazide (OM/AML/HCTZ) in 2112 participants with moderate to severe hypertension. Following 2 weeks of initial treatment with OM 40/AML 5/HCTZ 12.5 mg, participants not achieving BP goal were titrated to OM 40/AML 5/HCTZ 25 mg or OM 40/AML 10/HCTZ 12.5 mg on a randomized basis. At week 16, participants who did not achieve BP goal were further titrated to OM 40/AML 10/HCTZ 25 mg. At the end of the study, 44.5% to 79.8% of participants reached BP goal and the mean BP decreased from 168.6/100.7 mm Hg (baseline BP at randomization) to 125.0 to 136.8 mm Hg/77.8 to 82.5 mm Hg, depending on treatment. Long-term treatment with OM/AML/HCTZ was well tolerated and effective with no new safety concerns.