Evaluation of the Additional Efficacy, and Safety of Olmesartan Medoxomil 20mg / Hydrochlorothiazide 12.5mg in the Treatment of Chinese Patients With Mild to Moderate Essential Hypertension

Inclusion Criteria: * At Visit 3, mean seated diastolic blood pressure (SeDBP) ≥ 95 mmHg and \< 110 mmHg, AND mean seated systolic blood pressure (SeSBP) ≥140 mmHg and \< 180 mmHg * At Visit 4, mean SeDBP ≥ 90 mmH * No significant disorder in blood, kidney, liver, cardiovascular system or endocrinology system Exclusion Criteria: * Patients with known or suspect secondary hypertension * Unstable angina * History of acute myocardial infarct, or PTCA or surgical cardiac procedures 3 months before entry into this study * Prior or current congestive heart failure (NYHA grade III or IV), hypertrophic obstructive cardiomyopathy, valvular disease or rheumatic heart disease * Arrhythmia of clinical significance * Bilateral renal artery stenosis, isolated renal artery stenosis, post kidney transplantation * Acute glomerular nephritis * Gout sufferers, even with the normal serum uric acid at entry * Retinal hemorrhage /exudate * Type 1 diabetes mellitus * Uncontrolled type 2 diabetes mellitus * Hypovolemia * Patients with autoimmune disease