It is difficult to control morning hypertension in practical clinical situation. Angiotensin receptor blocker (ARB) and thiazide are suggested to be effective to maintain the antihypertensive effects for 24 hours. However, monotherapy sometimes is not enough to control blood pressure level in the next morning and there are little evidence of the combination therapy for morning hypertension. The investigators hypothesized that a losartan 50 mg/hydrochlorothiazide 12.5 mg combination drug, Preminent, is effective and safe for controling morning hypertension, compared with high-dose of losartan 100 mg, in Japanese. Patients with morning hypertension were randomized to preminent treatment group or high-dose losartan treatment group. The efficacy and safety were compared after 3-month treatment.

Inclusion Criteria:

• Clinical diagnosis of outpatients with morning hypertension (135/85 mmHg)
• Under treatment with any antihypertensive agents

Exclusion Criteria:

• Poorly controlled hypertension (DBP>120 mmHg)
• Poorly controlled diabetes (HbA1c>9.0%
• Gout or hyperuricemia (UA>8.0 mg/dL)
• Serum Cr>2.0 mg/dL
• Serum K>5.5 mmol/L
• Liver dysfunction (ALT>90 IU/L and/or g-GTP>14o IU/L)
• Secondary hypertension
• Patients who have contraindication for losartan and/or thiazide diuretics