We studied four patients with subacute to chronic varicella zoster virus (VZV) infection of the central nervous system (CNS). VZV infection was verified by detecting antibody to VZV in the cerebrospinal fluid (CSF). VZV caused myelitis in two patients and encephalitis in two patients. In one of the patients with VZV encephalitis, in addition to VZV IgM antibody, VZV DNA was found in the CSF. Among the four patients with VZV infection of the CNS, CSF antibody to VZV was the crucial diagnostic laboratory test which corroborated the clinical features, and indicated that VZV caused neurologic disease. In addition to looking for amplifiable VZV DNA in the CSF of patients with neurologic disease whose clinical and radiologic features suggest VZV infection, we also recommend a search for CSF antibody to VZV, particularly in patients with intervals of weeks to months between zoster and the onset of neurologic disease, or in those patients without rash in whom the tempo of illness is unknown.