Neurosonological examinations play an important role in the diagnosis of cerebrovascular disease. The target used to be limited to the extracranial carotid artery but is now extended to the intracranial arteries. Carotid artery ultrasound can evaluate not only the degree of stenosis but also the vulnerability of plaque. Transcranial Doppler can detect the micro-embolus in the intracranial artery. Transesophagial echocardiography and cruralvein ultrasound are indispensable to detect embolic source. Transesophagial echocardiography is able to detect thrombus, tumor and vegitation in the heart, patent foramen ovale (PFO) and atheroma of aorta. Because PFO is found rather commonly in healthy subjects, the detection of deep vein thrombosis (DVT) is essential for the diagnosis of paradoxical embolism. In stroke patients with PFO, RI venography can rarely detect DVT, while cruralvein ultrasound commonly detect DVT in small vein. The demand of neurosonological examinations is considered to increase more and more because of their non-invasiveness and convenience.