Abstract
Herpes simplex infection of the CNS may occur as part of a generalized infection with visceral involvement or with the CNS alone involved. Aseptic meningitis due to herpes simplex is rare, but necrotizing encephalitis is being recognized with increasing frequency. The distribution of lesions within the CNS and the mode of spread to and within the CNS are discussed. Serological tests indicate that some cases are due to primary infection and others due to re-activation. The importance of early diagnosis by electron and fluorescence microscopy and virus culture are discussed. The natural history and pathogenesis of herpes simplex and B virus are discussed.