Inclusion Criteria:

• Female or male patient with age ≧ 18 years old.
• Patient with mild to moderate uncomplicated essential hypertension, and the blood pressure not adequately controlled on existing antihypertensive treatment.
• Patient with sitting systolic blood pressure (sSBP)/ sitting diastolic blood pressure (sDBP) ≦ 180/110 mmHg at screening visit.
• For non-diabetic patient, sitting systolic blood pressure (sSBP) ≧ 140 mmHg or sitting diastolic blood pressure (sDBP) ≧ 90 mmHg at baseline visit; for diabetic patient, sitting systolic blood pressure (sSBP) ≧ 130 mmHg or sitting diastolic blood pressure (sDBP) ≧ 80 mmHg at baseline visit.
• Patient or his/her legally acceptable representative has signed and dated the informed consent form.

Exclusion Criteria:

• Known or suspected secondary hypertension.
• sSBP > 180 mmHg or sDBP > 110 mmHg at baseline visit.
• Patients taking more than two anti-hypertensive medications at the screening visit. (Fixed-dose combinations of two or more antihypertensive therapies will be counted as two or more antihypertensive medications.)
• Known NYHA functional class Chronic Heart Failure (CHF) III and IV.
• With a history of myocardial infarction, transient ischemic attack or cerebrovascular accident within the preceding 6 months, clinically significant valvular heart disease, or hepatic and/or renal dysfunction as defined by the following laboratory parameters
• SGPT (ALT) or SGOT (AST) > two times upper the limit of normal range
• Serum creatinine > 2.3 mg/dl or creatinine clearance < 30 ml/min

Other protocol-defined inclusion/exclusion criteria may apply