Normal findings from coronary angiography do not always show normal endothelial functions. An impaired flow-mediated dilation (FMD) can be a useful marker of the presence of endothelial dysfunction. Hypertension, left ventricular hypertrophy, hypercholesterolemia, and vasospastic angina pectoris can negatively affect FMD response. FMD responses of normal subjects and patients with coronary artery pathology were compared in a prospective cross-sectional study. Patients were divided into 3 groups. Group I patients had a positive exercise stress test and angiographically normal coronary arteries. Group 11 patients had angiographically significant coronary artery stenosis and stable angina pectoris. Group III had normal results from an exercise stress test and no chest pain. It was concluded that flow-mediated dilation response cannot predict coronary angiographic results. Patients with normal findings from coronary angiography may have impaired endothelial functions.