Lyme disease is a disease caused by the spirochete, Borrelia burgdorferi. It is transmitted to humans via a bite from an infected tick. It has several classic stages or categories of illness, including early localized disease, early disseminated disease, and late disease. The focus of this article is on the manifestations, diagnosis, and treatment of Lyme disease of the central nervous system. © 2003 Elsevier Inc. All rights reserved.