A 7-month-old infant had the infantile spasm syndrome, consisting of flexor and extensor spasms, developmental delay, and hypsarrhythmia. Corticotropin produced delay, and hypsarrhythmia. Corticotropin produced improvement in the clinical symptoms and reverted the generalized electroencephalographic abnormalities to more focal ones. Removal of a choroid plexus papilloma of the left lateral ventricle was followed by clinical recovery. One year later the child was normal developmentally and neurologically and was seizure free on anticonvulsant therapy.