The renin-angiotensin-aldosterone system (RAAS) plays a key role in the pathogenesis of cardiovascular disease. Blockade of this system results in a number of biologically important beneficial effects, including inhibition of the breakdown of bradykinin, reduction in blood pressure and inhibition of neuroendocrine activity, as well as reversal of endothelial dysfunction. Angiotensin-converting enzyme (ACE) inhibitors have an established role in the management of hypertension and heart failure. More recently, for instance in the HOPE trial, they have been investigated in patients with a history of coronary artery disease, stroke, peripheral vascular disease, or diabetes plus at least one other cardiovascular risk factor, but with preserved left ventricular function. Treatment with ramipril was shown to reduce cardiovascular events significantly, especially in patients who had diabetes. Two further ongoing trials – EUROPA (with perindopril) and PEACE (with trandolapril) – are described, which have important differences in trial design and which will further assess the protective effects of ACE inhibition in patients with stable coronary artery disease.