In the 1970s, pharmacological therapy interrupting the renin-angiotensin system was considered beneficial for patients with high-renin hypertension. This gave rise to the development of ACE inhibitors. Surprisingly, the ACE inhibitors proved to be effective not only in patients with high renin hypertension, but also in many patients with normal levels of plasma renin activity. At present ACE inhibitors have a significant position in a wide range of chronic illnesses such as atherosclerosis, hypertension, myocardial infarction, diabetic complications, stroke etc. They are combined safely with drugs like angiotensin receptor blockers, calcium channel blockers and thiazides with varying degree of benefits. Though they are safe drugs, patients need monitoring for renal insufficiency, hypotension, hyperkalemia etc. The safety of these drugs in paediatrics patients is not established. It is better to avoid these drugs during pregnancy.