A patient with atypical manifestations of Epstein-Barr Virus (EBV) encephalomyelitis is presented. The patient had unusual spinal fluid immunoglobulin abnormalities, the syndrome of inappropriate anti-diuretic hormone secretion, autonomic dysfunction and spinal arachnoiditis. The cisternal CSF, with a very high IgG level (34.3 mg/dl; normal less than 6.1) but a normal albumin content, displayed evidence of massive intrathecal immunoglobulin production. This was further confirmed by the presence of oligoclonal bands. These clinical manifestations have not previously been reported in encephalomyelitis associated with EBV infection.