Aliskiren is a potent, highly specific renin inhibitor with better oral bioavailability than earlier renin inhibitors and a long plasma half-life that makes it suitable for once-daily dosing. The efficacy and safety of aliskiren in treating hypertension has been studied in clinical trials both as monotherapy, comparing it with existing antihypertensive therapies, and in combination with other antihypertensive agents, including the diuretic hydrochlorothiazide, the angiotensin-converting enzyme inhibitor ramipril, and the calcium channel blocker amlodipine. From the extensive database acquired to date, it is clear that aliskiren is an effective antihypertensive agent, with once-daily administration resulting in dose-dependent systolic and diastolic blood pressure reductions. Combinations with existing antihypertensives are producing promising additional blood pressure-lowering effects.