We report a patient with herpes simplex virus (HSV) myelitis with a clinical history of rapidly progressive spinal cord dysfunction and extensive necrosis of the lumbosacral spinal cord at autopsy. The etiologic agent was HSV type 2. The close resemblance of the clinical features of this case to the syndrome of acute necrotizing myelitis emphasizes the need to recognize HSV myelitis as a cause of this syndrome, since it is diagnosable during life by culturing the CSF and is treatable.