AIMS AND OBJECTIVE : The blood supply of brain is of great importance because of the metabolic demands of the nervous tissue. A significant anastomosis, the Circle of Willis exist between the carotid and vertebral arterial systems. An understanding of the distribution of the arteries is very important. As the neurological signs depends on the site of lesion.

Material and methods: The study was conducted on 45 adult brain specimens of  both sexes in human cadavers.The collected specimens were preserved in 10% formalin.The Circle of Willis of each brain was dissected with care.

Results: Variations in posterior segment of  Circle of  Willis in brain specimens includes – hypoplasia and absence of arteries.

Conclusion: The posterior part of the circle is more anomalous than anterior part and the posterior communicating artery is the most anomalous segment when compared to all the segments of the arterial circle.Various diseases of  arteries of brain like cerebro – vascular attack, aneurysm, haemorrhage etc. are related to the anatomic patterns of  the Circle of Willis.The knowledge of which is of considerable help to neurosurgeons.