Surgery of the posterior fossa represents a technical challenge because of the proximity of the vessels of the cerebellum. If the arterial vascularization of the cerebellum is well known, the main arterial variations and the whole venous vascularization are probably under recognized. We describe the vascular organization and the main variations through photographs of colored latex perfused brains, obtained with a surgical microscope. The arterial vascularization of the cerebellum is based on three arteries which all originate from the vertebrobasilar system: the superior cerebellar artery (SCA), the anterior and inferior cerebellar artery (AICA), and the posterior and inferior cerebellar artery (PICA). The main arterial variations involve essentially the origin of these vessels. Concerning the SCA, its origin depends on the embryology. The AICA can arise from a common trunk AICA-PICA. It can be sometimes doubled and rarely absent. The PICA also can arise from a common trunk AICA-PICA and sometimes from the extradural segment of the vertebral artery. Concerning the venous organization, we distinguish the superficial and deep veins. The superficial veins drain the cerebellar cortex and transit on the surface of the cerebellum. The deep veins refer to the veins transiting in the fissures between the cerebellum and the brainstem. All these veins terminate as bridging veins that we can divide in three groups: a superior group emptying into the great vein, a posterior group emptying into the transtentorial sinus, and a lateral group ending into the superior petrosal sinus. The surgical implications are discussed.