Background and Purpose-We aimed to generate rigorous graphical and statistical reference data based on volumetric measurements for assessing the relative severity of white matter hyperintensities (WMHs) in patients with stroke. Methods-We prospectively mapped WMHs from 2699 patients with first-ever ischemic stroke (mean age=66.8±13.0 years) enrolled consecutively from 11 nationwide stroke centers, from patient (fluid-attenuated-inversion-recovery) MRIs onto a standard brain template set. Using multivariable analyses, we assessed the impact of major (age/hypertension) and minor risk factors on WMH variability. Results-We have produced a large reference data library showing the location and quantity of WMHs as topographical frequency-volume maps. This easy-to-use graphical reference data set allows the quantitative estimation of the severity of WMH as a percentile rank score. For all patients (median age=69 years), multivariable analysis showed that age, hypertension, atrial fibrillation, and left ventricular hypertrophy were independently associated with increasing WMH (0-9.4%, median=0.6%, of the measured brain volume). For younger (≤69) hypertensives (n=819), age and left ventricular hypertrophy were positively associated with WMH. For older (≥70) hypertensives (n=944), age and cholesterol had positive relationships with WMH, whereas diabetes mellitus, hyperlipidemia, and atrial fibrillation had negative relationships with WMH. For younger nonhypertensives (n=578), age and diabetes mellitus were positively related to WMH. For older nonhypertensives (n=328), only age was positively associated with WMH. Conclusions-We have generated a novel graphical WMH grading (Kim statistical WMH scoring) system, correlated to risk factors and adjusted for age/hypertension. Further studies are required to confirm whether the combined data set allows grading of WMH burden in individual patients and a tailored patient-specific interpretation in ischemic stroke-related clinical practice. Other risk factors such as diabetes mellitus, hyperlipidemia, atrial fibrillation, and smoking were inconsistently reported in the literature and seem less strongly associated with WMHs (Table I in the online-only Data Supplement). 3,[6][7][8][9][10] Despite a rapidly growing body of knowledge from population studies, substantial variability in WMH volume among individuals with similar cerebrovascular risk factors complicates a tailored interpretation of patient-specific implications of WMHs in daily clinical practice. [10][11][12] What is lacking is a comprehensive, quantitative study with substantial numbers, and robust methodology, which correlates WMHs to stroke risk factors so that the associations and interplay between risk factors can be better understood. Clinically, there have been no rigorous graphical and statistical reference data available for the individualized estimation of the relative severity (expressed as percentile ranks) of WMH burden adjusted for major risk factors (age/hypertension).In this study, we have combined (1) a la...