['We investigated the potential association between serum cholesterol levels and coronary microvascular function, using the index of microvascular resistance (IMR), in patients with coronary artery disease.', 'At the time of coronary angiography, IMR was measured in one or more epicardial vessel with an intermediate stenosis (>30%). Total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein cholesterol and triglyceride concentrations were measured before cardiac catheterization.', 'A total of 110 coronary arteries were investigated in 95 patients. The mean IMR was 26 ± 12 with evidence of microvascular dysfunction in 32 arteries (29%). A significant correlation was seen between IMR, total cholesterol (r=0.28, P=0.003) and LDL cholesterol (r=0.30, P=0.001). At multivariate analysis, LDL cholesterol was the only independent predictor of IMR, even after adjustment for the extent of epicardial coronary atherosclerosis and fractional flow reserve values.'] Are high cholesterol levels associated with coronary microvascular dysfunction?