The renin-angiotensin-aldosterone system (RAAS) plays an important role in blood pressure control and volume homeostasis. Inappropriate activation of the RAAS has been implicated in the pathogenesis of hypertension and related cardiovascular disease. Several classes of agents that block RAAS signaling have been shown to be effective antihypertensives and to have cardioprotective and renoprotective properties. Because blockade of the RAAS is incomplete with any of the currently available monotherapies, combinations of these agents have been tested and shown to provide additional clinical benefit in patients with hypertension and various forms of cardiovascular and renal disease. © 2010 Springer Science+Business Media, LLC.