Endothelial dysfunction is a primary event in atherogenesis and all known cardiovascular risk factors have been associated with endothelial dysfunction before atherosclerotic vascular disease manifests itself clinically. Pivotal to endothelial dysfunction is a disturbance in the function of endothelium-derived nitric oxide (NO). Recently, it could be shown that acute and chronic angiotensin-1 receptor antagonism reversed endothelial dysfunction in atherosclerosis. In experimental atherosclerosis, AT1 receptor blockade appears to have protective effects. Respective potential mechanisms include the prevention of endothelial injury, the augmentation of NO activity, the inhibition of lipid peroxidation and an antiproliferative effect. These findings together with the most recent data that losartan improves endothelial function and NO activity suggest that AT1 receptor antagonism may also be antiatherogenic in patients with atherosclerosis. Angiotensin II influences smooth muscle cell migration, hyperplasia, and hypertrophy. Angiotensin II also enhances production of local superoxide anion, which will inactivate nitric oxide. Inhibition of these reactions by the AT1-Blocker telmisartan may therefore interfere with atherosclerotic plaque formation.