The antihypertensive effect of the increased dose of angiotensin II receptor blocker (AII antagonist) is compared with that of the additional combined use of amlodipine in hypertensive patients with Type 2 diabetes mellitus, who have been treated with AII antagonist, the antihypertensive effect of which has been inadequate.

Inclusion Criteria:

• Patients with type 2 diabetes mellitus.
• Patients who have been treated by the single use of AII antagonist at usual for at least 8 weeks or patients who have been treated by the combined use of AII antagonist at usual doses and calcium channel blocker or a antihypertensive drug other than ACE inhibitors for at least 8 weeks.
• Patients who show a systolic blood pressure (blood pressure) > 135 mm Hg or a diastolic blood pressure > 85 mm Hg, which is measured (in a sitting position) on an outpatient basis at the time of start of the observation period, and show the mean (blood pressure level measured at home after getting up before the start of study) of systolic blood pressure > 130 mm Hg or diastolic blood pressure > 80 mm Hg measured at home after getting up for last 5 days during the last 2-week observation period.
• Patients whose consent is obtained at age 20 years or over.
• Patients whose consent is obtained from themselves in written form. With regard to 2) and 3), however, the case, in which the mean of the systolic blood pressure levels measured at home after getting up for last 5 days during the first 1-week observation period is > 180 mm Hg or the mean diastolic blood pressure level is > 110 mm Hg, is included in the present study.

Exclusion Criteria:

• Patients with secondary hypertension.
• Patients who show a systolic blood pressure > 180 mm Hg or diastolic blood pressure > 110 mm Hg on the measurement (in a sitting position) on an outpatient basis at the time of start of the observation period.
• Patients with severe hepatic dysfunction.
• Patients with severe renal dysfunction.
• Patients with a past history of hypersensitiveness to study drugs.
• Pregnant, lactating, and probably pregnant patients, and patients who want to become pregnant during the study period.
• Patients who have participated in the trial within 3 months before the start of the observation period or who attend the trial simultaneously with the present study.
• Other patients judged as being inappropriate for the subjects of the study by investigators.