Previous studies showed a weak correlation between endothelial function of the coronary arteries as assessed by acetylcholine and brachial artery vasomotion during reactive hyperemia. When the same stimulus was used, we obtained a strong correlation between flow-mediated dilation in the coronary and brachial arteries (r=0.78, p <0.001), so that noninvasive assessment of flow-mediated dilation in the brachial artery could be used as a surrogate measure for coronary artery endothelial function.