Hypertension is a major risk factor for cardiovascular morbidity and mortality and currently has been estimated at 30% of the US population. Of these, only 36.8% have their blood pressure reduced to recommended levels of lower than 140/90 mmHg for uncomplicated hypertension, or less than 130/80 mmHg for patients with diabetes mellitus or renal disease. Since monotherapy controls blood pressure in less than 50% of treated hypertensive patients, combination therapy is often required to bring blood pressure to the recommended levels of the 7th Joint National Committee report. One of the most effective and widely used combinations is the combination of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker with hydrochlorothiazide (HCTZ). Aliskiren, a new blocker of the renin–angiotensin system has been developed and approved by the US FDA on 18th January 2008 for the treatment of hypertension. Aliskiren is a direct inhibitor of renin, the rate-limiting enzyme for the production of angiotensin II, a powerful vasoconstrictive peptide. Several randomized clinical trials have demonstrated that aliskiren administered in single daily doses of 150, 300 or 600 mg alone and in combination with HCTZ 12.5 and 25 mg is effective in lowering blood pressure, and is safe and well tolerated. In this article, the pharmacokinetic and pharmacodynamic profile and the clinical application of aliskiren alone and in combination with HCTZ will be discussed