Inhibition of the renin-angiotensin system with angiotensin-converting enzyme inhibitors is well established as a treatment modality for hypertension and congestive heart failure. While converting enzyme inhibitors are well tolerated, they still have some side effects, which rightly or wrongly are attributed to the lack of specificity of the target enzyme for the renin-angiotensin cascade. The attempt is therefore made to inhibit the more specific enzyme renin or to block the angiotensin II receptor. While so far renin inhibitors are generally hampered by insufficient oral bioavailability, potent orally active angiotensin II antagonists are currently in clinical development. Both pharmacologic principles, renin inhibition and angiotensin II antagonism, have been shown to actively reduce blood pressure of hypertensive patients. It remains to be seen whether these newer compounds will be able to replace the converting enzyme inhibitors and exhibit even fewer untoward effects.