In most patients with hypertension, especially Stage 2 hypertension, adequate control of blood pressure (BP) is only achieved with combination drug therapy. When using combination therapy, antihypertensive agents with complementary mechanisms of action are recommended, for example, an angiotensin receptor blocker (ARB) in combination with hydrochlorothiazide (HCTZ), a beta-blocker + HCTZ, an ACE inhibitor + HCTZ, or a calcium channel blocker + an ACE inhibitor. One such combination is olmesartan medoxomil + HCTZ, which is available as fixed-dose, single-tablet combinations for once-daily administration. In clinical trials, olmesartan medoxomil/HCTZ reduced systolic BP (SBP) and diastolic BP (DBP) to a greater extent than either component as monotherapy. A clinical study in patients with Stage 1 or 2 hypertension showed that olmesartan medoxomil/HCTZ achieved a similar mean reduction in DBP, but a significantly greater mean reduction in SBP and higher rate of BP control (< 140/90 mmHg) than observed with losartan/HCTZ, at US/European-approved starting doses. In a non-inferiority trial, the antihypertensive efficacy of olmesartan medoxomil/HCTZ was comparable to that of atenolol/HCTZ. Furthermore, indirect comparisons have shown that olmesartan medoxomil/HCTZ compares favorably with other antihypertensive combination therapies, including other ARB/HCTZ combinations and amlodipine besylate/ benazepril. Olmesartan medoxomil/HCTZ is generally well tolerated. In conclusion, olmesartan medoxomil/HCTZ is an effective and well-tolerated combination antihypertensive therapy that results in significant BP reductions and BP control in many patients.