Purpose: Vertebral artery (VA) stump syndrome is described as one of the causes of posterior circulation ischemic stroke associated with VA occlusion. There are no reports of findings yielded by duplex ultrasound for diagnosing VA stump syndrome. The aim of the present study was to clarify the utility of duplex ultrasound for diagnosing VA stump syndrome. Subjects and Methods: Patients with acute posterior circulation stroke and VA proximal occlusion were diagnosed with VA stump syndrome. All patients underwent both duplex ultrasound and MRA unless contraindicated. CT angiography or conventional angiography was performed if possible. Results and Discussion: Seven patients were enrolled. On duplex ultrasound, an antegrade flow pattern was observed in four patients, although the culprit VA was occluded in the proximal portion. A to-and-fro pattern and delayed systolic upstroke flow were observed in the culprit VA in three and four patients, respectively. The collateral flow could be detected on duplex ultrasonography in four patients. Brain MRA revealed no abnormal findings in the vertebrobasilar arteries in two patients. Conclusion: Duplex ultrasound is useful for diagnosing VA stump syndrome, because duplex ultrasound can be used to evaluate flow and intravascular stasis.