Objective: To study differences in imaging utilization downstream to initial emergency department (ED) ultrasound examinations interpreted by radiologists versus nonradiologists. Methods: Using 5% Medicare Research Identifiable Files from 2009 to 2014, we identified episodes where the place of service was "emergency room hospital" and the patient also underwent an ultrasound examination. We determined whether the initial ultrasound was interpreted by a radiologist or nonradiologist and then summed all additional imaging events occurring within 7, 14, and 30 days of each initial ED ultrasound. For each year and each study window, we calculated the mean number of downstream imaging procedures by specialty group. Results: Of 200,357 ED ultrasound events, 163,569 (81.6%) were interpreted by radiologists and 36,788 (18.4%) by nonradiologists. Across all study years, ED patients undergoing ultrasound examinations interpreted by nonradiologists underwent 1.08, 1.22, and 1.34 additional diagnostic imaging studies at 7, 14, and 30 days, respectively (P <.01) compared with when the initial ultrasound examination was interpreted by a radiologist. From 2010 to 2014, the volume of downstream imaging for both radiologists and non radiologists significantly decreased, with each year resulting in 0.08 fewer imaging examinations (P <.001) 14 days after the ED ultrasound event. Despite that decline, differences in downstream imaging between radiologists and nonradiologists persisted over rime. Conclusion: Downstream imaging after an initial ED ultrasound is significantly reduced when the ultrasound examination is interpreted by a radiologist rather than a nonradiologist.