Lyme disease, the multisystem infectious disease caused by the tick-borne spirochete Borrelia burgdorferi, readily invades the central nervous system (CNS) and, in up to 15% of patients, causes symptomatic meningitis or involvement of the cranial or spinal nerves. The clinical evidence supporting an association between B. burgdorferi infection and cerebral vasculitis or stroke is tenuous at best. Unfortunately, parenchymal brain disease has not been reported in any animal model. Peripheral nerve disease occurs fairly commonly both in infected patients and in experimentally infected rhesus macaque monkeys. Although in both humans and monkeys this is a patchy multifocal disease (mononeuritis multiplex), with perivascular inflammatory infiltrates evident in biopsied nerves, in neither has there ever been evidence of a true vasculitis or significant vasculopathy. Thus, although neurosyphilis has been known for many years to cause vascular inflammation and damage, to date there is little proof that this occurs in Lyme disease.