Case 1.-A 4¡/¿-year-old white female was hos¬ pitalized because of a severe generalized convul¬ sion which occurred during the course of a mild febrile illness. Her birth, early development, and previous medical history had been without incident. No abnormal neurologic signs were noted, and ex¬ amination of her CSF was unremarkable. Five days later she developed delirium, intermittent stupor, restlessness, and spasticity. At the time of death, 16 days after onset, her temperature was 111 F (43.9 C). Death was due to bilateral bronchopneumonia. The brain was grossly normal and weighed 1,190 gm (normal for this age). Micro¬ scopically there was widespread neuronal damage, characterized by swelling, pallor, vacuolization, or complete disappearance, most severe in the frontal and temporal lobes. Rod cells and astrocytes were increased throughout the cerebral cortex. Similar changes were present in the thalamus and olivary and dentate nuclei. The cerebellar cortex and white matter in all areas were normal. There was no * Cited by permission of H. D. Palmer, MD, Denver, and previously published as a clinicalpathological report.8