The Varicella zoster virus may affect the central nervous system (CNS) as a complication of herpes zoster (HZ). A series of neurological syndromes are described and, on the basis of a review of the literature and two illustrative case histories, the symptomatology, pathogenesis, therapeutic possibilities and the diagnostic difficulties in HZ-associated cerebral vasculitis and HZ-associated encephalitis are reviewed. Progressive multifocal encephalopathy in immune-insufficient individuals is briefly mentioned. The diagnosis is most frequently established on the basis of the clinical picture when the characteristic symptoms develop in connection with cutaneous HZ. A long latent period may result in defective recognition of the connection. Immuno-suppression and dissemination are critical determinants for the course of the condition but, in immune-competent individuals, the morbidity and mortality are low. Treatment with acyclovir is employed to an increasing extent with good results but the conditions are rare and clinically controlled investigations are not available. It is important that the possibility of HZ-associated CNS-disease is borne in mind, in view of the therapeutic possibilities. The pathogeneses of these complications is little understood but there is increasing evidence that a direct viral invasion is the mechanism responsible. A post-infectious immune-mediate mechanism is also another popular opinion.