We have reviewed 23 cases of varicella-zoster virus infection of the central nervous system in patients with the acquired immunodeficiency syndrome, previously reported in the literature, including 11 from our own series. This allowed us to identify 5 clinico-pathological patterns which could occur simultaneously. In most cases, viral proteins or viral genome were identified using immunocytochemistry or in situ hybridization. Multifocal encephalitis involves predominantly the white matter and is likely to be due to haematogenous spread of the infection. Ventriculitis may have variable appearance according to the course of the disease. In one incipient case, the ependymal lining appeared irregular with foci of infected ependymal cells some of which protruded into the ventricular lumen; in other instances, there was acute or chronic necrosis of the ventricular wall with marked vasculitis. Acute haemorrhagic meningo-myelo-radiculitis with necrotising vasculitis may be associated with ventriculitis and results from shedding of infected ependymal cells into the ventricular lumen and secondary seeding of the cerebrospinal fluid. Focal necrotising encephalitis or myelitis usually follows cutaneous herpes zoster in the corresponding dermatoma and is considered to result from neural spread from the diseased trigeminal or dorsal root ganglion. Vasculopathy involving leptomeningeal arteries and causing cerebral infarcts is associated with meningitis in most cases. These findings are in keeping with the observation in other immunocompromised patients, that varicella-zoster virus spread to the central nervous system may follow different routes. Our study tends to show that varicella-zoster virus infection of the central nervous system is more frequent in the acquired immunodeficiency syndrome than previously suspected and suggests this diagnosis must be considered systematically in cases of encephalitis, ventriculitis, focal myelitis, acute myeloradiculitis and cerebral infarcts in these patients, since an efficient treatment is available.