© 2015 Society of Cardiovascular Computed Tomography. Background: Left ventricular (LV) volume and mass have prognostic relevance. Overall size of the left ventricle as it appears in noncontrast CT is a composite of the ventricular volume and myocardial mass. We describe a method to estimate the LV size using a single cross-section in noncontrast CT and determined normal ranges on the basis of a large population cohort. Methods: The Multi-Ethnic Study of Atherosclerosis with 6814 participants from 4 ethnicities who were free of known cardiovascular disease and enrolled between 2000 and 2002 form the basis of our analysis. LV size was calculated from a single cross-sectional slice obtained by either nonenhanced electron beam or multidetector CT. LV size was adjusted to body surface area to obtain the LV size index, which was adjusted for age, sex, race or ethnicity, hypertension, hyperlipidemia, and diabetes. Results: There were significant differences in LV size index by race which were further influenced by age and sex. Higher values were noted in men in all ethnic groups across all age groups. Similarly, LV size index uniformly decreased with age across all ethnic and sex categories. Caucasians had the lowest and African Americans had the highest LV size index across all age and sex categories. In multivariate regression analyses adjusted for age, sex, race or ethnicity, hypertension, hyperlipidemia, smoking, and diabetes mellitus, the significant differences were noted between male vs female (median difference, 17.5 cc/m2; P < .001), ethnic groups (Caucasian, reference group; Asian, 3.7 cc/m2; African American, 8.3 cc/m2; and Hispanic, 5.6 cc/m2; P < .001), and age groups (45-54years, reference group; 55-64years,-5.2 cc/m2; 65-74years,-11.4 cc/m2; and 74-84years,-12.5 cc/m2). Conclusions: This study provides normative values for LV size as determined from a single, nonenhanced CT cross-section and indexed to body surface area, and it demonstrates that the LV size index varies by age, sex, and ethnic background.