We describe the complexity of oscillating thrombus (OT) pathology determined by carotid ultrasonography (US) in one patient with cardioembolic stroke and in another with idiopathic carotid artery dissection. The OT disappeared over time under B-mode US observation in both patients. However, Doppler flow evaluation revealed occlusion indicating the absence of internal carotid artery recanalization. Oscillating thrombus is a rare and specific finding, and follow up by carotid US is useful for observation. Further information about OT is required.