In the reseach we used 30 encephalon of zebuine bovine fetuses, previously injected with colored latex and fixed in formlin solution of 20 percent, followed by careful dissections. The basilar artery has its origin off the convergnce of the caudal branch of he carotid artery of the encephalon (both right and left sides) in a hundred per cent of the cases, showing progressively a smaller caliber a facial-caudal way, which suggests that maybe the blood flow goes along in this way, where there are some collateral branches of the basilar artery, as it follows: caudal cerebellar artery, arteries to the bridge and to the medulla oblongata