Inclusion Criteria:

• Subjects who are 18 years of age or older,
• Treated with antihypertensive therapy and have a post-washout mean sitting clinic SBP of ≥ 160 and ≤ 190 mm Hg on Day 1 (day prior to randomization) or are treatment naïve and have a mean clinic SBP of ≥ 160 and ≤ 190 mm Hg at the screening visit and on Day 1.
• Women must be surgically sterile, postmenopausal, or if of childbearing potential, not pregnant or lactating and do not intend to become pregnant during the course of the study and agree to use adequate contraception during the course of the study.
• Subjects who are capable of understanding and willing to comply with the protocol requirements, willing to sign the informed consent prior to undergoing any study related procedures, willing to discontinue current antihypertensive medication for a 3 to 4-week washout period, and have clinical laboratory results within the reference range for the testing.

Exclusion Criteria:

• Subjects who have hypersensitivity to angiotensin II receptor blockers or thiazide-type diuretics.
• Previously been randomized in a TAK-491 study, a mean clinic diastolic blood pressure (DBP) (sitting, trough) > 119 mm Hg.
• Work a night (third) shift.
• Have an upper arm circumference < 24 cm or > 42 cm.
• Secondary hypertension of any etiology.