Angiographic evidence of stenotic damage in the proximal segment of the subclavian artery, together with retrograde flow in the vertebral artery on that side, was first reported by Contomi in 1960, but the patient had no neurological deficit. The syndrome was named “subclavian artery steal syndrome”. This syndrome can also be seen in the head and arm stem lesions because the retrograde blood also enters the subclavian artery, so it can also be called “subclavian artery piracy syndrome”. Subclavian artery piracy syndrome refers to the narrowing or occlusion of the subclavian artery or the unnamed artery in the proximal segment of the beginning of the vertebral artery and the return of blood from the contralateral vertebral artery to the affected vertebral artery via the basilar artery to reconstitute the blood supply to the distal segment of the affected subclavian artery. The symptoms are dizziness, blurred vision, unstable walking, and in some cases, headache, head and occipital pain, or hearing loss. In some cases, the “stolen blood” may appear in the subclavian artery or vertebrobasilar artery, or even in the cerebral hemispheric artery, which may lead to mild hemiplegia and aphasia. In practice, if a regurgitant vertebral artery is found, the affected subclavian artery or the unnamed artery should be further examined. Even if the right unnamed artery and the beginning of the left subclavian artery cannot be examined directly, it may indicate a stenosis or occlusion on the side of the regurgitant vertebral artery. In another case, in which the blood pressure difference between the brachial arteries is >2.6-4.0 kPa (2030 mmHg) bilaterally, the radial artery pulsation is diminished or absent (pulselessness), and Doppler ultrasound reveals stenosis or occlusion of the subclavian artery or the unnamed artery, then the vertebral artery must be examined again to clarify whether there is a subclavian artery steal syndrome. In the case of vertebral artery regurgitation due to stenosis of the subclavian artery or the unnamed artery, reverse flow can be restored to the affected vertebral artery after arterial dilatation or other surgical treatment of the stenosis.