The ACE inhibitors have proved to be a significant advance in the therapy of cardiovascular disease. All act in an identical manner by binding to the catalytic site of ACE, but differ in the degree and the length of time of ACE inhibition in different tissues. Although the clinical significance of this is unclear, it raises the exciting possibility of designing ACE inhibitors with tissue selective effects. The mode of action of ACE inhibitors is complex, and further research in this area is necessary particularly with regard to the role of bradykinin. ACE inhibitors can now be regarded as first line therapy for congestive cardiac failure, for patients with left ventricular dysfunction or hypertensive left ventricular hypertrophy and to prevent ventricular remodeling after myocardial infarction when left ventricular function is impaired. ACE inhibitors are the treatment of choice in patients with normotensive or hypertensive diabetic nephropathy. In essential hypertension, ACE inhibitors are at least as effective as other agents in lowering blood pressure and the results of long term clinical trials currently underway will determine whether this translates into a reduction in cardiovascular morbidity and mortality.