OBJECTIVE : To compare the use of medical imaging (x-ray [XR], CT, ultrasound, and MRI) in the emergency department (ED) for adult patients of different racial and ethnic groups in the United States from 2005 to 2014. METHODS : We performed a multilevel stratified regression analysis of the National Hospital Ambulatory Medical Care Survey ED Subfile, a nationally representative database of hospital-based ED visits. We examined race (white, black, Asian, other) and ethnicity (Hispanic versus non-Hispanic) as the primary exposures for the outcomes of ED medical imaging use (XR, CT, ultrasound, MRI, and any imaging). We controlled for other potential patient-level and facility-level determinants of ED imaging use. RESULTS : Approximately half (48.8%) of the 225,037 adult patient ED visits underwent imaging; 36.1% underwent XR, 16.4% CT, 4.1% ultrasound, and 0.8% MRI. White patients received imaging during 51.3% of their encounters, black patients received imaging during 43.6% of their encounters, Asians received imaging during 50.8% of their encounters, and other races received imaging during 46% of their encounters. As compared with white patients, black patients had decreased adjusted odds of receiving imaging in the ED (odds ratio [OR] = 0.86, 95% confidence interval [CI]: 0.84-0.89). Comparatively, black patients had a lower odds of CT scan (OR = 0.80, 95% CI: 0.77-0.83) or MRI (OR = 0.74, 95% CI: 0.65-0.85). Hispanic patients and Asian patients had a higher odds of receiving ultrasound (OR = 1.36, 95% CI: 1.27-1.44 and OR = 1.25, 95% CI: 1.10-1.42), respectively. CONCLUSIONS : We observed significant racial and ethnic differences in medical imaging use in the ED even after controlling for patient- and facility-level factors.