Purpose: To assess the reproducibility of HR-MRI for the identification of MCA atherosclerotic plaque components and quantification of stenosis. Materials and methods: Seventy-three consecutive subjects who initially had ischemic stroke or asymptomatic MCA stenosis (>50%) were enrolled in the study. All subjects were scanned using 3.0 T MRI. Two independent readers reviewed all images and one reader reevaluated all images four weeks later. The tissue components of plaques were analyzed qualitatively and the vessels were quantitative measured. Results: HR-MRI displayed the artery wall and lumen clearly. The intra-observer reproducibility was excellent for the identification of plaques (kappa [kappa] = 0.96; 95% CI: 0.83-1.04) and contrast enhancement (kappa = 0.89; 0.78-0.95); it was substantial for intra-plaque hemorrhage (kappa = 0.79; 0.57-0.96) and the fibrous cap (kappa = 0.65; 0.42-0.86). The inter-observer reproducibility was excellent for plaques (kappa = 0.92; 0.73-1.06), substantial for contrast enhancement (kappa = 0.80; 0.65-0.93), intra-plaque hemorrhage (kappa = 0.68; 0.47-0.92) and moderate for the fibrous cap (kappa = 0.58; 0.44-0.79). Both intra-observer and inter-observer reproducibility were excellent for quantitative vessel, lumen and wall measurements with intraclass correlation coefficients ranging from 0.91 to 0.97 and 0.87 to 0.96, respectively. However, vessel and wall areas and the intervals defined by the Bland-Altman plots were wide in comparison to the mean. Conclusions: The identification of MCA atherosclerotic plaque components and the quantification of vessel and lumen measurements are reproducible. The reproducibility is overall acceptable. HR-MRI may provide a useful tool for clinical risk evaluation in MCA atherosclerosis. (C) 2013 Elsevier Ireland Ltd. All rights reserved.