Coronary spasm is induced by acetylcholine, serotonin, ergonovine, or histamine, all of which cause vasodilation when the endothelium is intact, and is promptly relieved by nitroglycerin, which vasodilates through the direct action on smooth muscle. Endothelial dysfunction is therefore possibly involved in the pathogenesis of coronary artery spasm. The aim of this study was to determine whether endothelium-dependent vasodilation is impaired in the peripheral arteries of patients with coronary spastic angina. Flow-dependent vasodilation of the brachial arteries during reactive hyperemia after the transient arterial occlusion was examined by using the high-resolution ultrasound technique in 35 patients with coronary spastic angina and 35 controls. Flow-dependent vasodilation of the brachial arteries was impaired in patients with coronary spastic angina compared with controls (5.9% +/- 4.2% vs 9.6% +/- 3.4%, p < 0.001) although the percent increase in blood flow during reactive hyperemia was not different between the two groups. The dilator response to nitroglycerin was preserved in patients with coronary spastic angina compared with controls (18.6% +/- 5.1% vs 16.2% +/- 3.9%, p < 0.04). The results indicate that endothelium-dependent vasodilation of the brachial arteries is impaired in patients with coronary spastic angina. Thus endothelial vasomotor dysregulation may also be present in the systemic arteries as well as coronary arteries in patients with coronary spastic angina.