The purpose of this study is to evaluate the safety and efficacy of fixed combination of amlodipine(5mg or 10mg) and losartan (50 mg or 100 mg), amlodipine and losartan alone in reducing blood pressure. The study will investigate the dose response relationship for the combinations and monotherapies.

Inclusion Criteria:

• Patients aged between 18 and 75
• Patients with essential hypertension {95 mmHg ≤ sitDBP< 115 mmHg at the end of placebo run-in treatment period}

Exclusion Criteria:

• Patients with mean sitSBP ≥ 200 mmHg
• Patients with known hypersensitivity to Dihydropyridine or angiotensin II receptor blockers
• Patients with secondary hypertension or suspected secondary hypertension
• Patients with malignant hypertension
• Patients who have received any medications with possible interactions with study drugs
• Patients with uncontrolled diabetes
• Patients with severe heart disease or severe cerebrovascular disease
• Patients with clinically significant hematological test results, renal disease (serum creatinine) or liver disease (ALT or AST)
• Patients with a history of malignant disease
• Patients with a history of autoimmune disease
• Women with a positive pregnancy test result, breast feeding or intention of pregnancy during the trial
• Patients inappropriate to be included in study population due to other reasons at the discretion of the investigator