OlmeSartan and Calcium Antagonists Randomized (OSCAR) Study

Inclusion Criteria: * Outpatients aged 65 years or older, and less than 85 years (at the time of informed consent), regardless of sex * Current antihypertensive treatment with monotherapy * SBP ≥ 140mmHg or DBP ≥ 90mmHg in a sitting position on two measurements on two clinic visits * At least one of the following risk factors: * Diabetes mellitus Type 2; * History of cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage, or transient ischemic attack (more than 6 months before giving informed consent); * Diagnosis of asymptomatic cerebrovascular disease; * History of myocardial infarction (more than 6 months before giving informed consent); * Diagnosis of angina pectoris or heart failure (New York Heart Association \[NYHA\] functional classification I or II); * Diagnosis of left ventricular hypertrophy (thickness of the wall of interventricular septum ≥ 12mm on echocardiography or Sv1+Rv5 ≥ 35mm on electrocardiography before informed consent); * Diagnosis of aortic aneurysm; * History of aortic dissection (more than 6 months before giving informed consent); * Diagnosis of arteriosclerotic peripheral arterial obstruction (Fontaine classification from 2 to 4); * Serum creatinine: 1.2-2.5mg/dL (male); 1.0-2.5mg/dL (female); * Proteinuria: ≥ +1 (or ≥ 0.3g/g･Cr. estimated from 24-hour urine collection or random urinary protein corrected by urine creatinine). Exclusion Criteria: * Secondary hypertension or malignant hypertension * Heart failure (NYHA functional classification III or IV) * Required treatment for malignant tumor * Serious liver or renal dysfunction (serum creatinine \> 2.5mg/dL or with dialysis treatment) * Not appropriate for change to the test drugs from current therapy for hypertension or coronary diseases (i.e. calcium channel blockers, β-blockers, thiazide diuretics, etc.) * History of serious adverse drug reactions to angiotensin II receptor blockers or calcium channel blockers * Patients with other serious reasons (i.e. illness, significant abnormalities, etc.) that investigators judge inappropriate for the study