['Hypertension impairs coronary endothelial cell function, coronary microvascular function and the coronary flow (CF) reserve (CFR). Angiotensin II receptor blockers (ARBs) have been reported to possibly improve coronary endothelial function and coronary microvascular function. The purpose of this study was to determine whether treatment with the ARB olmesartan was more effective for improving CFR than the calcium channel blocker amlodipine.', 'Twenty patients with untreated essential hypertension (M/F = 13/7, aged 55.6 ± 11.6 years) were randomly assigned to treatment with either olmesartan (n = 10) or amlodipine (n = 10) for 6 months. CF was measured in the proximal left anterior descending artery by magnetic resonance imaging before and during intravenous infusion of adenosine. CFR was calculated as the ratio of the hyperemic to baseline diastolic peak flow before and after 6 months of treatment.', 'The extent of systolic blood pressure reduction was similar in both groups (-40.0 ± 19.1 vs. -48.8 ± 14.7 mm Hg, p = 0.26). The olmesartan group showed significant improvement of CFR (from 1.9 ± 1.0 to 3.1 ± 1.1, p = 0.005), but this did not occur in the amlodipine group.'] Does olmesartan improve coronary flow reserve of hypertensive patients using coronary magnetic resonance imaging compared with amlodipine?