Objective: The purpose of the study was to examine the variations in arteries contributing in the formation of Circle of Willis in adult human brains from Nagpur region of Maharashtra. Material and methods: The external diameters of posterior cerebral artery (PCA), posterior communicating artery (PCOM), internal carotid artery (ICA), anterior cerebral artery (ACA) and anterior communicating artery (ACOM) in 50 male and 50 female brains were measured with verniercaliper. Photographs were taken and results studied by applying t.test and z test. Results: In this study 99% circles were complete.One circle with absent right sided PCA was found.Hypoplasia was noted in about 37 to 39% circles for PCA, about 39% circles for PCOM, 20% circles for ICA, 44% circles for ACA and 44% circles for ACOM.6% ACOM showed duplication. Regarding gender differences, hypoplasia of vessels overall was found to be more common in females than males. Duplication of ACOM was another finding found in female circles only. Conclusion: In present study it appears that there do exist variation in arteries forming circle of willis. Some preponderance to some arteries is also found in this study. Again male and female comparison is also helpful as it has revealed some significant findings. Such knowledge of circle of willis is of utmost importance to surgeons before performing any surgery related to ICA and also important for physicians to lead to conclusions in stroke and infarct patients where MRI can be used to find out status of arteries.