Extracranial and transcranial Doppler and duplex sonographic findings in six patients with internal carotid artery dissection proven by angiography is reported. Extracranial Doppler analysis showed occlusion without a recordable signal from the internal carotid artery at any level or stenosis with accelerated flow in the high cervical segment. Transcranial Doppler findings demonstrated the hemodynamic consequences of the internal carotid artery occlusion or stenosis with collateral flow across the circle of Willis and also showed the dampened pulse wave of the middle cerebral artery ipsilateral to the dissection. In duplex sonography, the indirect signs indicating internal carotid artery dissection were a patent carotid bifurcation and proximal internal carotid artery segment but with no or only a short systolic flow signal. Atherosclerotic wall changes were absent, an important finding that suggests nonatherosclerotic stenosis or occlusion. Direct signs making the diagnosis likely were a tapering of the internal carotid artery lumen distal to the bulb, an irregular membrane crossing the vessel lumen, and the demonstration of a true lumen with flow and a false one without flow. While cerebral angiography is still considered the gold standard, ultrasound may become the primary modality for early diagnosis. Doppler and duplex examinations help to indicate angiography and are the methods of choice for follow-up investigations. They clearly demonstrate spontaneous recanalization with normalization of carotid circulation or, in case of persistent occlusion, improvement of collateral blood supply. Sequential examinations may prove helpful to determine the duration of anticoagulant treatment.