To determine the effect of nerve growth factor (NGF) on the neurotoxicity of herpes simplex virus type 1 (HSV-1) in vivo, direct intrastriatal injection of HSV-1 in rats was followed by continuous intracerebral infusion of NGF or vehicle solution for 7 days. The mean volume of HSV-1-mediated brain tissue destruction in NGF-treated animals was significantly smaller than that in vehicle-treated animals at 1 week. Immunohistochemical staining for HSV-1 confirmed the presence of cells harboring the virus at the primary site of injection and at secondary sites of distant spread, with no significant difference in HSV-1 distribution between NGF- and vehicle-treated animals. We conclude that intrastriatal infusion of NGF locally protects against HSV-1-mediated neurolysis, but does not affect HSV-1 dissemination in the brain.