The authors report an adult individual found to have very unusual origins of additional left and right pericallosal arteries that are normally only branches of the anterior cerebral artery. These vessels both arose from the vertebrobasilar system. The right accessory pericallosal artery was found to originate from the ipsilateral posterior inferior cerebellar artery and the left accessory pericallosal artery was found to originate from the ipsilateral posterior cerebral artery. To our knowledge, this variation has not been previously reported. The embryological and surgical implications of this finding are discussed. © Springer-Verlag 2007.