A patient with X-linked hypoganunaglobulinemia developed chronic meningoencephalitis. ECHO virus type 5 was repeatedly cultured from cerebrospinal fluid (CSF). Infusions of high-titer, specific plasma resulted in clinical improvement, but failed to eradicate the virus. After more intensive plasma infusions, the virus could not be cultured from the CSF. The patient died 8 months after institution of intensive therapy. The cause of death was unknown. Autopsy showed persistence of perivascular and meningeal inflammation. Specific anti-ECHO-virus-5 plasma was shown to be more effective in lowering CSF ECHO-virus titers than was plasma without anti-ECHO-virus antibody.