The renin-angiotensin system (RAS) plays a pivotal role in the progression of some forms of hypertension and cardiovascular disease. The development of angiotensinconverting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) has provided physicians with effective and well-tolerated inhibitors of the RAS. However, it remains open to question whether ACE inhibitors and ARBs have fully delivered the reductions in cardiovascular risk that we might have expected. There is little doubt that in conditions such as chronic and acute heart failure or diabetic nephropathy these drugs have provided significant protection. But, in patients with high-risk hypertension, for instance, the anticipated benefits of RAS blockade have been less obvious. This article provides a critical assessment of the results of clinical trials of ACE inhibitors and ARBs across a variety of clinical conditions and assesses the potential need for new methods for blocking the renin system, including the use of renin inhibitors.