BACKGROUND AND OBJECTIVES: Angiotensin-converting enzyme (ACE) inhibitors have been shown to improve the endothelial dysfunction and prevent the development of atherosclerosis in animal models. We performed this study to investigate the effects of the ACE inhibitor, ramipril, on carotid atherosclerosis and endothelial dysfunction of the brachial artery in patients with coronary artery disease (CAD). SUBJECTS AND METHODS: We studied 69 subjects with a mean age of 59yrs, and divided them into two groups according to ramipril use (39 patients with ramipril and 30 without). Using a double-blind, randomized, prospective design, we measured the flow-mediated vasodilatation (FMD) of the brachial artery and intima-media thickness (IMT) of the carotid artery, prior to, and 1, 3 and 6 months following coronary angiograms in CAD patients. RESULTS: The FMD was significantly increased in the ramipril group from 4.6+/-2.2% baseline to 5.3+/-2.5% at the 1 month follow-up (p<0.05), but at the 3 and 6 month follow-ups no significant changes were found. There were no significant differences in the FMD between the two groups at any of the follow-up periods, and no changes in the IMT were found in relation to time for either group. CONCLUSION: Ramipril improved the endothelial dysfunction in patients with CAD for the first month; however this effect did not persist 3 or 6 months after taking ramipril. Ramipril had no effect on the atherosclerotic vascular changes to the IMT of carotid arteries.