A nested polymerase chain reaction was used for the detection of Epstein-Barr virus DNA in 1 patient with encephalitis, and in 1 patient with myelitis. Epstein-Barr virus DNA was detected in cerebrospinal fluid samples obtained at the onset of neurological symptoms in both patients, and serological findings indicated ongoing Epstein-Barr virus infection. In the patient with encephalitis, herpes simplex virus type 1 DNA was transiently detected in the cerebrospinal fluid, while Epstein-Barr virus DNA was still present on day 44 after admittance. Single-photon emission computed tomography in this patient indicated a frontal bilateral hypoperfusion. The diagnostic value of polymerase chain reaction on cerebrospinal fluid and serum samples for Epstein-Barr virus infections of the central nervous system is emphasized.