Fifty four cerebrospinal fluid samples obtained from as many immunocomponent patients with disorders of the central nervous system were investigated for the presence of herpesvirus DNA by nested polymerase chain reaction in order to determine an etiological diagnosis. Four of these samples proved positive for the presence of Epstein-Barr virus DNA (7.4%). The result of this diagnostic study is reported to draw insiders' attention to the possible presence of EBV in cerebrospinal fluid from patients with central nervous system diseases.