Herpes simplex virus (HSV) encephalitis is an acute febrile encephalopathy usually characterized by disordered mentation, fever, headache, and focal seizures. We have described a patient with HSV encephalitis whose initial illness was manifested solely as a seizure disorder. Consequently, the diagnosis was not made until late in the hospital course. This atypical presentation of HSV encephalitis is emphasized to facilitate recognition of this disorder and to prompt early diagnostic brain biopsy so that appropriate antiviral therapy can be instituted.