ARB and CCB Longest Combination Treatment on Ambulatory and Home BP in Hypertension With Atrial Fibrillation -Multicenter Study on Time of Dosing (ACROBAT)

Inclusion Criteria: 1. Hypertensive patients who meet the following conditions: Patients who meet any of the following standards of blood pressure after administration of 40 mg/day telmisartan or 5 mg/day amlodipine for 4 weeks: \- Blood pressure at hospital visit: Systolic blood pressure is 140 mmHg or higher, and/or diastolic blood pressure is 90 mmHg or higher. (average of 3 measurements obtained at a scheduled visit) \- Blood pressure at home: Systolic blood pressure is 135 mmHg or higher, and/or diastolic blood pressure is 85 mmHg or higher. (average of measurements for the 5 days prior to drug assignment \[4 measurements per day in total: 2 in the morning and 2 before bedtime\]) 2. Patients with atrial fibrillation detected on an electrocardiogram within the last 2 years prior to obtaining informed consent. 3. Age: 20 years old or older (at time of informed consent) 4. Sex: male or female 5. Clinical classification: Outpatient 6. Patients who give written consent of agreement to voluntarily participate in the clinical study. Exclusion Criteria: 1. Patients with serious liver and/or kidney disease 2. Patients with history of allergy to telmisartan or amlodipine 3. Patients receiving antihypertensives other than telmisartan or amlodipine during observation period 4. Patients diagnosed with persistent atrial fibrillation or chronic (permanent) atrial fibrillation. 5. Patients with atrial fibrillation caused by irreversible illness (e.g., heart surgery, pulmonary embolism, or hyperthyroidism) 6. Patients with average systolic blood pressure at hospital visit higher than 180 mmHg during observation period. 7. Patients with New York Heart Association (NYHA) class III-IV heart failure, patients with heart failure requiring hospitalization, or patients with poor left ventricular function. 8. Patients who have stroke or cardiac infarction within 6 months before giving consent. 9. Patients planning to undergo pulmonary artery ablation surgery or any surgical procedure (including PCI). 10. Patients who are breast-feeding, pregnant, possibly pregnant, or plan to become pregnant. 11. In addition, patients who are determined as not eligible by their study doctor.