A previously normal, 5-year-old boy developed a rapidly progressive neurological illness three days following diagnosis and treatment of a streptococcal pharyngitis. He had quadriparesis, then developed pseudobulbar palsy and respiratory failure, and died eight weeks later. At postmortem examination, the neuropathological findings were diagnostic of subacute necrotizing encephalomyelopathy, a disease primarily of infancy, which when present in older children almost always follows the course of a chronic neurological illness.