PROBE Parallel 6-week Treatment Comparing Telmisartan/Hydrochlorothiazide (HCT) (40/12.5 or 80/12.5) With Losartan/HCT (50/12.5) Using Ambulatory Blood Pressure Monitoring (ABPM)

A Prospective, Randomised, Open-Label, Blinded-Endpoint, Parallel Group 6-week Treatment Study Comparing Telmisartan Combined With Hydrochlorothiazide (40 mg/12.5 mg or 80 mg/12.5 mg) Tablets With Losartan Combined With Hydrochlorothiazide (50 mg/12.5 mg) Tablets Using Ambulatory Blood Pressure Monitoring in Patients With Mild-to-Moderate Hypertension

To demonstrate that Telmisartan combined with Hydrochlorothiazide (MICARDIS® HCT) is superior to Losartan with Hydrochlorothiazide (Hyzaar®) in lowering blood pressure in mild-moderate hypertensives.

Inclusion Criteria:

1. Ability to provide written informed consent in accordance with GCP and local legislation.
2. Mild-to-moderate hypertension defined as a mean seated DBP of >= 95 mm Hg and <=l to 109 mm Hg, measured by manual cuff sphygmomanometer at Visit 2.
3. Male or Female >= 18 years.
4. Ability to stop any current antihypertensive therapy without risk to the patient (investigator's discretion).
5. 24-hour ABPM mean DBP of >= 85 mm Hg at Visit 3.

Exclusion Criteria:

1. Pre-menopausal women (last menstruation <= 1 year prior to signing informed consent) who

   • are not surgically sterile, or are
   • nursing, or
   • are of child-bearing potential and are NOT practicing acceptable methods of birth control, or do not plan to continue practicing an acceptable method throughout the study. Acceptable methods of birth control include IUD, oral, implantable or injectable contraceptives. No exception will be made.

2. Night shift workers who routinely sleep during the daytime and whose work hours include midnight to 4:00 A.M.

3. Mean seated SBP >= 180 mm Hg or mean seated DBP >= 110 mm Hg during any visit or the placebo run-in phase.

4. Known or suspected secondary hypertension (i.e. pheochromocytoma).

5. Hepatic and/or renal dysfunction as defined by the following laboratory parameters: a)SGPT (ALT) or (SGOT) AST less than two times the upper limit of normal range, or b)Serum creatinine greater than 2.3 mg/dL (>203 mico mol/l).

6. Bilateral renal artery stenosis, renal artery stenosis in a solitary kidney, post-renal transplant patients or patients with only one kidney.

7. Biliary obstructive disorders.

8. Clinically relevant sodium depletion, hypokalaemia or hyperkalaemia.

9. Uncorrected volume depletion.

10. Primary aldosteronism.

11. Hereditary fructose intolerance.

12. Congestive heart failure (NYHA functional class CHF III-IV).

13. Unstable angina within the past 3 months prior to signing the informed consent form.

14. Stroke within the past 6 months prior to signing the informed consent form.

15. Myocardial infarction or cardiac surgery within the past 3 months prior to signing the inform consent form.

16. PTCA (percutaneous transluminal coronary angioplasty) within the past 3 months prior to signing the informed consent form.

17. Sustained ventricular tachycardia, atrial fibrillation, atrial flutter or other clinically relevant cardiac arrhythmias as determined by the investigator.

18. Hypertrophic obstructive cardiomyopathy, aortic stenosis, hemodynamically relevant stenosis of the aortic or mitral valve.

19. Patients with insulin-dependent diabetes mellitus whose diabetes has not been stable and controlled for at least the past 3 months as defined by an HbA1C >= 10 Percent.

20. Patients who have previously experienced symptoms characteristic of angioedema during treatment with ACE inhibitors or angiotensin II receptor antagonists.

21. History of drug or alcohol dependency within 6 months prior to signing the informed consent form.

22. Chronic administration of any medications known to affect blood pressure, except medication allowed by the protocol.

23. Any investigational therapy within 1 month of signing the informed consent form.

24. Known hypersensitivity to any component of the study drugs (placebo, telmisartan, hydrochlorothiazide or losartan).

25. Any clinical condition which, in the opinion of the investigator would not allow safe completion of the protocol and safe administration of trial medication.

26. Concomitant use of lithium or cholestyramine or colestipol resins (potential drug interactions with hydrochlorothiazide).

27. History of non-compliance with prescribed medication.

28. Inability to comply with protocol.