The vasculature of the 29 roots of the trigeminal nerve was examined after india ink and gelatin had been injected into the vertebrobasilar arterial system. The trigeminal arteries were most often noted to arise from the superolateral pontine branch of the basilar artery (89.66%), and from the peduncular cerebellar branch of the anterior inferior cerebellar artery (75.86%). The trigeminocerebellar artery supplied two roots (6.89%) of the trigeminal nerves. The number of trigeminal arteries ranged from two to six, and their diameters ranged from 100 to 510 microns. Anastomoses among them were seen in 37.93% of the cases. The arteries formed the vascular rings around 58.61% of the roots. The motor portion of the trigeminal nerve most often received blood from the superolateral pontine artery (79.31%). The same artery most commonly supplied the rostral part of the sensory portion, which corresponded to the ophthalmic division of the trigeminal nerve. The superolateral artery, together with the inferolateral pontine artery and the peduncular cerebellar branch of the anterior inferior cerebellar artery, irrigated the middle part of the sensory portion, which corresponded to the maxillary division. The caudal part of that portion, which corresponded to the mandibular division, was commonly perfused by the peduncular cerebellar branch of the anterior inferior cerebellar artery. In this article, we discuss the possible clinical significance of the anatomic data observed.