Cytomegalovirus (CMV) infections are common and severe complications of HIV infection. The virus involves the nervous system, causing encephalitis, polyradiculomyelitis and peripheral neuropathies. Due to their limited sensitivity, traditional virological approaches, such as virus isolation or antigen detection in the CSF are useful only in limited instances, e.g. CMV polyradiculopathy. The aetiological diagnosis of these disorders relies on the analysis of cerebrospinal fluid by PCR and quantitative PCR may be important to establish the extent of CNS lesions and to monitor the efficacy of antiviral treatments. CMV is susceptible to various antivirals, including ganciclovir, foscarnet and cidofovir. CMV infections of the nervous system, in particular encephalitis, however, show only a poor response to standard treatments. Drug combination treatments i.e. ganciclovir plus foscarnet, are currently under evaluation in clinical trials.