This article reviews definitions and normal anatomy and physiology of canine and feline cerebral vasculature. The pathophysiology of cerebrovascular disease (CVD), which results from disturbance of cerebral blood supply, is described, along with its common causes and correlative findings. The general clinical presentation of companion animals is described, although specific neurologic abnormalities depend on the neuroanatomic location of the disrupted blood supply. Current and future diagnostic approaches are described, including ancillary testing for predisposing factors. Acute and chronic management of patients with CVD is discussed. The prognosis for dogs and cats with acute CVD is generally considered good.