Objective　To analyze CT angiography features of arterial fenestrations concerning with vertebro-basilar arteries and its branches in an effort to improve our understanding of this anomaly.　Methods　 Between November 2007 and July 2009, 2051 head and carotid CT angiographies were performed in our hospital, and 4.2% (88 fenestrations) were diagnosed in 86 patients. The CTA of those 86 patients were evaluated retrospectively to determine the incidence, location and configuration of the fenestration and the relationship between the anomaly and the surrounding structures. The coexisting abnormalities were also evaluated.　Results　48 fenestrations of basilar artery (2.34%) were detected in this study. The fenestrations were at the proximal portion of basilar artery trunk in 31 cases, and at vertebrobasilar junction in 16 cases. 37 fenestrations of vertebral artery (1.8%) were detected, with 19 anomalies at the intracranial level. In which, 16 fenestrations were at the extracranial level, and 2 at the atlantoaxial level and the intracranial segment of the artery. 2 fenestrations of the posterior cerebral artery and 1 fenestration of inferior cerebellar artery were found. 15 small fenestrations (less than 2 mm) presented foramen-like shape. 37 of 73 large fenestrations simulated an "ok" hand sign, and 36 showed partial duplication type of fenestration. 1 aneurysm associated with basilar artery fenestration and 3 aneurysms near the other arteries were found. In 7 patients there were additional cerebrovascular anomalies, 2 of them were associated with anterior cerebral artery fenestrations, while other 5 coexisted with origin variation in left vertebral arteries (emanated from aortic arch).　Conclusions　64-slice CTA of the cranio-cervical arteries is a rapid, intuitive, and accurate method for demonstrating vertebrobasilar artery fenestration and its coexisting abnormalities. Diagnosis of this anatomic variation prior to surgery and intervention may be helpful for procedures choice and decreasing the risk of operation.