1. Experimental and clinical studies have demonstrated the efficacy of inhibitors of angiotensin-converting enzyme (ACE) in a variety of cardiovascular diseases. Both structural and functional improvements have been reported. 2. Hypertension, atherosclerosis, congestive heart failure or ageing are accompanied by endothelial dysfunctions. The vasoactive endothelium-derived relaxing factors, nitric oxide, endothelium-derived hyperpolarizing factor and prostacyclin, could be involved, depending on the pathology. 3. Some of the beneficial effects of ACE inhibitors may be due to the augmented release of these endothelial factors resulting from the protection of locally produced bradykinin, particularly at the endothelial level.