The use of angiotensin-converting enzyme (ACE) inhibitors has been generally beneficial in the treatment of many clinical conditions characterized by a significant degree of cardiovascular and renal involvement. Most of the available data on the benefits of ACE inhibitors have come from well-conducted large clinical trials that have provided much information supporting the use of ACE inhibitors, in agreement with the basic principles of evidence-based medicine. In particular, ACE inhibitors improve blood pressure control in patients with hypertension and have proved to be beneficial in patients with left ventricular (LV) systolic dysfunction and chronic congestive heart failure (CHF). Improved survival rates after the use of ACE inhibitors have been also demonstrated in patients with acute myocardial infarction (MI), whether or not the condition is complicated by acute CHF. More recently, some studies have demonstrated the ability of ACE inhibitors (particularly fosinopril) to prevent the long-term development of CHF in patients treated acutely during MI and without baseline LV dysfunction. ACE inhibitors appear to improve the long-term prognosis of patients with coronary artery disease (CAD) and to reduce the occurrence of re-infarction, as demonstrated in the Studies of Left Ventricular Dysfunction (SOLVD) trial and the Survival and Ventricular Enlargement study (SAVE). Finally, a protective role for ACE inhibitors has been reported even in diabetic hypertensive patients, in whom such agents can significantly reduce the occurrence of major cardiovascular events (CAD and stroke) with a pattern that is largely independent of blood pressure control and is not observed with the use of calcium antagonists. These data confirm the strong involvement of the renin-angiotensin system in the pathophysiology of vascular diseases and strongly support the role of ACE inhibitors as drugs for present and future therapy.