['Endothelial dysfunction is closely related to cardiovascular events. Several studies have documented that angiotensin II type 1 receptor blockers (ARB) improve peripheral endothelial dysfunction. However, the effect of ARB on coronary endothelial function remains elusive. The purpose of this study was to ascertain the beneficial effects of ARB on human coronary artery endothelial function.', 'Twenty-seven patients were randomly assigned to either the candesartan group (n=14) or the control group (n=13) and followed for 12 months. Coronary blood flow velocity was measured in the left anterior descending artery without stenosis using an intracoronary Doppler-tipped guide-wire. We evaluated coronary endothelial function as the coronary blood flow velocity reserve (CFR), which was defined as the percent change in the coronary blood flow velocity after an intracoronary acetylcholine infusion. At baseline, the CFR in both groups was below 300%, implying that these patients had endothelial dysfunction. After treatment with candesartan for 6 months, the CFR increased significantly from 199 ± 20 to 337 ± 27% (P<0.001), whereas the CFR did not change in the control group (194 ± 32 vs. 185 ± 41%, P=0.52). During 12 months of observation, the cardiovascular event-free survival rate of the patients with an increased CFR was significantly greater than the rate in patients with a decreased CFR (P=0.02). Moreover, the cardiovascular event-free survival rate was greater in the candesartan group than in the control group (P=0.04).'] Does candesartan improve impaired endothelial function in the human coronary artery?