We describe a young urban boy with atypically fulminant subacute sclerosing panencephalitis (SSPE). He had measles at 3 years of age despite receiving measles immunization in infancy. The literature describing acute SSPE is reviewed and summarized. This report reiterates the need to include SSPE as a diagnostic possibility in acute encephalopathic processes. The dismal prognosis of SSPE further emphasizes the need for measles vaccination and revaccination of all children who are initially immunized at an age of less than 15 months.