A 57-year-old diabetic man died of a rapidly ascending necrotizing myelitis. Autopsy results proved that the etiologic agent was herpes simplex virus type 2 (HSV2). The clinical findings, autopsy immunohistopathology, and electron-microscopy suggest that either primary HSV2 infection or reactivation of HSV2 infection within dorsal root ganglia was followed by spread to the spinal cord. Viral infection of the CNS occurred by direct extension and led to death by involvement of the brainstem. Although there is only one previous report of HSV2 myelitis in the literature, our findings suggest that HSV2 might be a more common etiologic agent of necrotizing myelitis. Because CSF cultures are usually negative, viral inclusions are not usually seen, and morphologically identifiable virions are exquisitely rare, previous cases were probably descriptively diagnosed as acute ascending necrotizing myelitis without etiologic identification.